LIBRARY OF CONGRESS. 



©^Hp* Ixip^rw 

Slielf.....;...v^c>jS 

UNITED STATES OF AMERICA. 



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SPECTACLES 



EYEGLASSES 



THEIR FORMS MOUNTING AND 
PROPER ADJUSTMENT 



/ 



BY 



R. J. PHILLIPS, M.D. 

ii 
ADJUNCT PROFESSOR OF DISEASES OF THE EYE, PHILADELPHIA POLYCLINIC AND COLLEGE 
FOR GRADUATES IN MEDICINE ; OPHTHALMIC SURGEON TO THE 
PRESBYTERIAN HOSPITAL IN PHILADELPHIA, ETC. 



SECOND EDITION, REVISED 

WITH 49 ILLUSTRATIONS 



PHILADELPHIA \J!^^oi^ 

P. BLAKISTON, S O N ^'T^^^Ii^i^^ 



10 12 WALNUT STREET 
1895 



■ f^^s 



Copyright, 1895, by P. Blakiston, Son & Co. 



PRESS OF WM. F. FELL &. CO., 

1220-24 SANSOM ST., 

PHILADELPHIA. 



r 



PREFACE TO THE SECOND EDITION. 



Since the publication of the first edition the author has 
frequently had the pleasure of hearing from students of 
ophthalmology that they had found in it information of 
which they had often experienced the need, but which is 
not usually supplied by works on their special subject. In 
preparing the present edition the aim has been to add an 
account of such real and lasting improvements in spectacles 
as have been introduced since the first edition was published. 

The portions relating to prisms have been revised and 
rewritten in accordance with the now well established re- 
form in the numeration of prisms. Several new tables and 
a few new cuts have been added. Simplicity of diction has 
been kept in view, to the end that the book might present 
its subject, not only fresh, but in a form readily intelligible 
to the elementary student. 

August y i8g^. 



PREFACE TO THE FIRST EDITION. 



This little wojk is the outgrowth of the instruction on 
the subject of prescribing spectacle frames which has been 
given to successive classes at the Philadelphia Polyclinic 
and College for Graduates in Medicine. The book, like 
the teaching referred to, is intended to supplement studies 



IV PREFACE TO THE FIRST EDITION. 

in refraction, and to give the student that knowledge of 
the correct placing of the glasses before the eyes without 
which the most painstaking measurement of the refraction 
will frequently fail of practical result. With the populari- 
zation, as one may call it, of ophthalmology in the pro- 
fession, many physicians who prescribe glasses are com- 
pelled, by the lack of skilled opticians in their neighborhood, 
to themselves furnish the spectacles to the patient. To 
these, it is believed, the knowledge which I have endeavored 
to impart in these pages will prove especially useful. 

Of late years much advance has been made in the art of 
making efficient, comfortable, and handsome contrivances 
for holding glasses before the eyes, and the increased use 
of prismatic and c)4lindrical lenses has given the fitting of 
the frames increased importance. Text-books of refraction 
remain, however, almost devoid of reference to the subject, 
the scant literature of which is scattered through opticians' 
trade publications and a few medical periodicals. Free 
application has been made to such sources, and the in- 
debtedness incurred duly acknowledged in the text. 

My thanks are due to my friend and instructor, Dr. 
Edward Jackson, for many valuable suggestions in writing 
this treatise, and, indeed, for directing my attention to the 
need of a book on spectacles. 

Dr. George M. Gould kindly furnished me with some 
references used in the introduction, and I am indebted to 
Messrs. Wall & Ochs, Bonschur & Holmes, and J. W. 
Queen & Co. for a number of cuts. 

March ^ i8g2. 



CONTENTS. 



PAGE 

Introduction, 17 

I. General Considerations, 26 

The Material of Frames, 26 

The Component Parts of Spectacles, 27 

The Lenses : Their Material and Manufacture, 28 

Eye Wires, Temples, and Bridges, 38 

The Different Patterns of Spectacles, • • ^S 

The Varieties of Eyeglasses, 46 

Spectacles for Cosmetic Effect, 48 

II. The Principles of Spectacle Fitting, 49 

Centering and Decentering, 49 

Prismatic Effect of Decentering, 51 

Normal Lateral Centering, 55 

Normal Vertical Centering, 56 

Distance of the Glasses from the Eyes, 57 

Perpendicularity of the Plane of the Lenses to the Visual Axes, . 58 

Periscopic Glasses, 62 

III. Prescription of Frames, 65 

The Measurements Required, 65 

Obtaining the Interpupillary Distance, 67 

Height of the Bridge, 71 

Relation of the Top of the Bridge to the Plane of theLenses, . . 72 

Width of Base, 73 

Prescription of Eyeglasses, ^ 75 

IV. Inspection and Adjustment of Spectacles and Eyeglasses, 76 

Proving the Strength of Lenses^ 76 

Phacometers, 77 

Neutralization of Spherical Lenses, 79 

Neutralization of Cylindrical Lenses, . . 80 

V 



VI CONTENTS. 

Inspection and Adjustment of Eyeglasses, Etc. — Continued. page 

Neutralization of Sphero-cylindrical Lenses, 8i 

Locating the Optical Center, 82 

Finding the Apex of a Prism, 83 

Measuring the Strength of a Prism, 84 

Detection of Scratches, Specks, Flaws, Etc., 90 

Irregularity of the Refracting Surfaces, 91 

Adjusting Spectacle Frames, 91 

Adjustment of Eyeglasses, 97 

The Care of Spectacles, . 100 



LIST OF ILLUSTRATIONS. 



FIGURE PAGE 

1. Position of the parts of spectacles, 28 

2. Position of the parts of eyeglasses, 28 

3. Sections of Lenses, 32 

4. Optician's lens- grin ding lathe, 34 

5. Concave toric and concave cylindrical lens, 38 

6. Frameless bifocal spectacles, 39 

7. Forms of spectacle bridges, 41 

8. Ovals, showing the sizes of spectacle eyes, 43 

9. Forms of bifocal glasses, 44 

10. Extra front, 45 

11. Forms of rigid frame eyeglasses, 47 

12. Modern frameless eyeglasses, 47 

13. Patterns of the offset guard, 48 

14. Spectacles with lenses decentered '* in," 50 

15. Section of a normally centered lens, 52 

16. Decentered lens, showing prismatic effect, 52 

17. Profile view of the face, showing the "natural'* position for the 

spectacle bridge, 57 

18. Top of bridge " out " from plane of the lenses, 58 

19. Top of bridge " in " from plane of the lenses, 58 

20. Spectacles facing directly forwards, 60 

21. Spectacles facing downwards and forwards, 60 

22. Spectacles facing inwards, 61 

23. Front and back of a convenient spectacle rule, 66 

24. Method of measuring the height of a spectacle bridge, 68 

25. Simplest method of measuring the interpupillary distance, .... 68 

26. Maddox pupil localizer, 69 

27. Method of using the Maddox pupil localizer, 69 

28. Meyrowitz pupillometer, 70 

29. A common form of pupillometer, 71 

30. Method of measuring the distance of the bridge " out," 72 

31. Method of measuring the distance of the bridge " in," 73 

vii 



Vlll LIST OF ILLUSTRATIONS. 

FIGURE PAGE 

32. Mr. Brayton's lens measure, 78 

33. Apparent displacement of lines caused by rotating a cylinder, ... 80 

34. Method of finding the axis of a cylindrical lens, 80 

35. Ready method of locating the optical center of a lens, S^ 

36. Mode of marking the apex of a prism, 83 

37. A prism improperly held, . S^ 

^S. Implement for measuring the refracting angle of prisms, 88 

39. Method of determining the deviating angle of prisms, 89 

40. Rotation of a lens within its eye- wire, 91 

41. Bend at the junction of the eye-wire and bridge, 92 

42. Showing the planes of the lenses crossing each other, 92 

43. Bend of the bridge, 93 

44. Inequality of corresponding angles of the bridge, 93 

45. Angles on one side of the bridge too small ; on the other too large, . 93 

46. Proper fitting of hook temples, 96 

47. A common but incorrect shape of the nose pieces of eyeglasses, . . 97 

4'8. Eyeglasses v/ith nose pieces of correct shape, 98 

49. The points at which eyeglasses are to be adjusted, 99 



SPECTACLES AND EYEGLASSES. 



INTRODUCTION. 

At what time man invented lenses and discovered the 
aid which they are capable of lending to vision is a matter 
beyond our knowledge. It is tolerably certain that they 
were known to civilizations earlier than ours. The late 
Wendell Phillips was wont to assert that spectacles were 
among the things known to the ancients. Though it 
might be difficult to sustain this assertion as regards spec- 
tacles in the present meaning of the term, the evidence in 
relation to their acquaintance with the essential element of 
spectacles, the lens, is reasonably convincing. This evi- 
dence was, for the most part, discovered by Sir Austen 
Henry Layard among the ruins of old Nineveh, and is of 
the most interesting character. Among the articles which 
he unearthed was a specimen of trajisparent glass (a small 
vase or bowl) with a cuneiform inscription fixing its date 
quite accurately to the latter part of the seventh century 
B. C. ('' Discoveries Among the Ruins of Nineveh and 
Babylon, etc.," by Austen H. Layard, New York, 1853, P- 
196.) This is the most ancient known specimen of trans- 
parent glass, though Egypt furnishes it of a date only a 
century later, and opaque or colored glass was manufac- 
tured at a much earlier period, some specimens of the 
fifteenth century B. C. still enduring. However, the ancient 
nations were not compelled to wait for transparent glass 

17 



1 8 SPECTACLES AND EYEGLASSES. 

in order to invent lenses, as they had in rock crystal a 
material admirably adapted to that purpose, and Layard 
was so fortunate as to discover such a lens in Nineveh. 
{Ibid., p. 197.) Sir David Brewster, who examined this 
lens, described it as being plano-convex, of a diameter of 
one and a half inches, and capable of forming a tolerably 
distinct focus at a distance of four and a half inches from 
the plane side. It is interesting to note farther in regard 
to this, the oldest lens in existence, that it is fairly well 
polished, though somewhat uneven from the mode in which 
it was ground, which Brewster concludes was not upon a 
spherical surface, but by means of a lapidary's wheel, or 
some method equally rude. Another evidence of the use 
of lenses has come down to us from antiquity. Upon 
record-cylinders of old Nineveh, and on engraved gems 
and stones of Babylon, Egypt, and other sources which 
long antedate the Christian era, are characters and lines of 
such delicacy and minuteness as to be undecipherable 
without the aid of a magnifying lens. Taking these facts 
in conjunction, the statement that some of the properties 
of lenses were known to and utilized by the ancients, the 
old record writers of Assyria, for instance, may be regarded 
as almost as well demonstrated as though it were made 
of a modern engraver, and we were to step into his work- 
shop and find his magnifying loup lying beside his work. 

The testimony as to their use by the Romans during 
their supremacy is of a less conclusive character. The 
statement frequently made that the -Emperor Nero used a 
concave jewel to assist his sight rests upon some obscure 
sentences in Pliny. That author says : '' Nero could see 
nothing distinctly without winking and having it brought 
close to his eyes." (Bk. 11, Chap. 54, Riley's Trans.) 
In another place, speaking of the emerald, smaragdus^ he 



INTRODUCTION. I9 

says : *' In form these are mostly concave, so as to reunite 
the rays of light and the powers of vision. * * * 
When the surface of the smaragdus is flat, it reflects the 
image of objects in the same manner as a mirror. The 
Emperor Nero used to view the combats of gladiators upon 
(with, or by means of) a smaragdus." (Bk. 37, Chap. 17.) 
The mention of the reflecting properties of the emerald 
immediately before the statement of Nero's use of it, with 
the alternative renderings of the Latin ablative, smaragdo^ 
make the supposition that Nero used the emerald as an 
eyeglass uncertain, though in view of his clearly described 
nearsightedness, the conjecture is probable enough. 

Lenses appear to have been unknown in Europe during 
the first twelve hundred years of the Christian era, though 
the Saracen Alhazen, who died in Cairo in 1038, has left 
books showing his acquaintance with them. These books 
were brought to Europe at a very early period, and the 
manuscripts yet exist, some in the Bodleian library, and 
another portion in that of the University of Leyden. It 
was probably from them that the early writers obtained 
their first hints of the science of optics, on the revival of 
learning in the fourteenth and fifteenth centuries. It is 
worthy of note that Alhazen was born at Bassora, at the 
head of the Persian Gulf and less than five hundred miles 
from the spot where, sixteen hundred years before, had 
stood the palace of the Assyrian kings in the ruins of 
which Sir Henry Layard found the lens of crystal. It 
might, perhaps, be plausibly maintained that in the countries 
about the Tigris some knowledge of optics, and of convex 
lenses, has persisted without eclipse from the most remote 
ages. 

The earliest European reference to our subject occurs in 
the writings of Roger Bacon, who died in 1292, and to 



20 SPECTACLES AND EYEGLASSES. 

whom the invention of the instrument he describes is 
sometimes accredited. Bacon's glass was apparently a large 
plano-convex lens, probably what we now call a reading 
glass, intended to be held in the hand, and of it he says : 
" This instrument is useful to old men and to those that 
have weak eyes; for they may see the smallest letters 
sufficiently magnified." Spectacles proper — that is, glasses 
mounted so as to retain themselves upon the face — appear 
to have been invented in Florence somewhere between 
1280 and the close of the thirteenth century. Dr. Samuel 
Johnson is said to have expressed surprise that the inventor 
of such useful articles has found no biographer. Doubtless 
among the thousands for whom the discovery has kept 
open the sources of knowledge there would be found one 
to pay this tribute to the fame of his benefactor were the 
identity of the latter a matter of certainty. But, unfortu- 
nately, our evidence on the point is of the most fragment- 
ary character. We are told in a general way that the 
Chinese have for ages employed spectacles for the relief of 
defective eyesight. This is, perhaps, to be regarded as 
only another instance of the exercise of that claim to 
priority which the Chinese are known to extend over every 
good and perfect gift. The longest chase signally fails to 
bring the tradition to bay in any fact. The tomb of Sal- 
vinus Armatus, a Florentine nobleman who died in 13 17, 
is said to bear an inscription to the effect that he was the 
inventor. If epitaphs enjoyed a less equivocal reputation 
for truthfulness he would doubtless be held in grateful 
remembrance as the man who has lengthened youth by 
postponing old age ; and, like Joshua, kept back the night 
until the day's work was done. 

Whoever the inventor, Alessandro di Spina, a monk of 
Florence who died in 13 13, is generally accredited with 



INTRODUCTION. 21 

having made public the use of spectacles, and by several 
Florentine writers of that time we find them mentioned 
and recommended. Pissazzo, in a manuscript written in 
1299, says: *' I find myself so pressed by age that I can 
neither read nor write without those glasses they call 
spectacles, lately invented, to the great advantage of poor 
old men when their sight grows weak." Friar Jordan, of 
Pisa, in 1305 says that *' it is not twenty years since the art 
of making spectacles was found out, and is, indeed, one of 
the best and most necessary inventions in the world." 

An early mention of spectacles, or, in the language of 
that time, *' a spectacle," occurs in *' The Canterbury Tales," 
where Chaucer makes the Wife of Bath use the metaphor : — 

Povert (poverty) full often when a man is lowe, 
Makiih him his God and eek himself to knowe 
Povert a spectacle is, as thinkith me, 
Through which he may his verray frendes se. 

There is in existence in the church of Ogni Santi, 
Florence, an old fresco by Domenico Ghirlandajo, repre- 
senting St. Jerome, and dated 1480. The Saint is portrayed 
seated at a desk, apparently deep in the composition of one 
of the blasts against the Heretics for which he was famous. 
Upon a peg at the side of the desk, together with the ink- 
horn and a pair of scissors, hangs a small handleless /^V/^:^- 
nez. The glasses are round and framed in dark bone, and 
in the bridge, also of bone, is a hinge. Though the artist 
seems to have been little impressed by the fact that St. 
Jerome died in the year 420, nearly nine centuries before 
spectacles were invented, the mounting and material repre- 
sented in these early spectacles are worthy of note as 
showing their form in Ghirlandajo's time, and probably 
that in which they originated. 

In the early references to spectacles it is the convex lens 



22 SPECTACLES AND EYEGLASSES. 

for the use of the presbyopic which is mentioned. Concave 
lenses were probably introduced soon afterward ; by whom 
we do not know. Glasses were at that time and for long 
afterward selected and used empirically ; since it was not 
until the year 1600 that the astronomer, Johann Kepler, 
who may be regarded as the father of ophthalmology, made 
known in what manner the rays of light were refracted by 
the media of the eye and form an image upon the retina. 
Kepler went farther, and showed how convex and concave 
glasses influence this refraction, and to him is therefore 
due the honor of first scientifically treating this subject. 

It must have been early discovered that there is a more 
or less close relation between the age of the wearer and 
the strength of the convex glass required, and the baneful 
theory was soon developed that this relation is constant, 
and that it would be ruinous to use a lens '' too old for the 
eyes," a superstition from which the public is even yet not 
fully emancipated. We find it rampant in Pepys' time, 
preventing his oculist. Dr. Turberville,* from giving that 
gentleman a proper correction for his accommodative 
asthenopia, of which the diary gives an accurate picture, 
and losing to the world many a priceless page. Pepys 
says (June 30, 1668) : '' My eyes bad, but not worse, only 
weary with working. ^ ^ ^k j ^^^ come that I am not 
able to read out a small letter, and yet my sight good, for 
the little while I can read, as ever it was, I think." But 
Dr. Turberville warns him against glasses too' old for him, 
and so the diary is closed, and Pepys in a last pathetic 
entry resigns himself to coming blindness ; and yet the 



* Daubigny Turberville ; created M.D. at Oxford in 1660. He practiced 
with great reputation as an oculist in London. His monument yet remains in 
Salisbury Cathedral, where he was buried. 



INTRODUCTION. 23 

convex lenses were at his hand, ready to dissipate the mists 
before him and enable him to " gaze upon a renovated 
world." 

Improvement in spectacles appears to have been slow. 
The world waited more than two centuries after Kepler 
for another signal advance. Sir David Brewster is said to 
have discovered his own astigmatism ; that is, he dis- 
covered that vertical and horizontal lines were not equally 
well seen by him at like distances, but the phenomenon 
was not explained and the observation faded from view. 
It remained for George Airy, the astronomer, to rediscover 
astigmatism, which he did about 1827, to determine that 
the curvature of the cornea was greater in one diameter 
than in another at right angles to the first, and to invent 
the cylindrical lens for the correction of the condition. Mr. 
Airy's right eye was myopic, while in the left he had com- 
pound myopic astigmatism. By a careful comparison of 
the appearance of objects when viewed with each eye 
singly, and a study of the effect of concave lenses held 
before the left eye upon lines crossing each other at right 
angles, he was able to conclude that the refraction of that 
eye differed in different planes. Mr. Fuller, an optician of 
Ipswich, made, under Airy's direction, a concave sphero- 
cylindrical lens which satisfactorily corrected his refractive 
error. Thus was the last great discovery in spectacles 
accompHshed, — a bit of work for completeness leaving 
nothing to be desired, and of not sufficiently acknowledged 
importance to humanity. 

Benjamin Franklin invented bifocal spectacles. Since 
this statement is supposed by many to rest on tradition 
only, it may be of interest to quote a portion of a letter of 
Franklin's which bears upon the point. The letter is ad- 
dressed to George Whately, of London, and is dated 



24 SPECTACLES AND EYEGLASSES. 

Passy, 23d May, 1785. In it Dr. Franklin says : " By Mr. 
Dolland's saying that my double spectacles can only serve 
particular eyes, I doubt he has not been rightly informed 
of their construction. I imagine it will be found pretty 
generally true that the same convexity of glass through 
which a man sees clearest and best at the distance proper 
for reading, is not the best for greater distances. I there- 
fore had formerly two pairs of spectacles which I shifted 
occasionally, as in traveling I sometimes read, and often 
wanted to regard the prospects. Finding this change 
troublesome and not always sufficiently ready, I had the 
glasses cut and half of each kind associated in the same 
circle. By this means, as I wear my spectacles constantly, 
I have only to move my eyes up or down, as I want to see 
distinctly far or near, the proper glasses being always 
ready. This I find more particularly convenient since my 
being in France. ^ ^ ^ " ^" Th^ Complete Works of 
Benjamin Franklin." Ed. by John Bigelow, New York, 
1888.) 

We may infer from the context that the invention took 
place before FrankHn went to France, which was in the 
latter part of 1776. As he was born in 1706, the necessity 
for a double glass would first arise about 1750, and the 
invention therefore took place somewhere between this 
date and that of the journey to France. 

The frames in which spectacles were mounted continued 
to be very clumsy affairs until the beginning of this cen- 
tury, when light metal frames were introduced in place of 
the earlier devices of bone, horn, or shell. Their later 
evolution has generally been along the lines of improved 
mechanical construction and increased lightness and beauty. 
It would be difficult to mention an article which plays a 
more important part in modern life than do spectacles, or 



INTRODUCTION. 2$ 

one which plays its part more acceptably. It is scarcely 
possible to estimate them at their true worth, or to imagine 
our condition without them. Deprived of their aid, most 
men would be too old for work at fifty, and purblind at 
sixty. For us all, as an old writer quaintly observes, 
" they keep the curtain from falling until the play has come 
to an end." 



I. GENERAL CONSIDERATIONS. 

By far the most generally useful method of placing 
glasses before the eyes is by spectacle frames, though the 
eyeglass, or pince-nez, has advantages in some cases, from 
the facility and quickness with which it may be placed in 
position or removed. The superiority of eyeglasses in 
appearance and becommgness is another point not unworthy 
of consideration, as the glasses will surely be more con- 
stantly worn if they are becoming than if they are not so. 
Moreover, the patient is justly entitled to the correction of 
his refractive error with as little injury to his appearance as 
possible. The disadvantages of eyeglasses are, that for 
constant wear they are seldom so comfortable as spectacles ; 
that on some faces it is nearly impossible to keep them in 
place ; while, where the contained glass is cylindrical or 
prismatic, the rotary motion which it is possible for the 
glass to take is a serious and sometimes fatal objection to 
their adoption. 

Lorgnettes and single eyeglasses, or quizzing glasses, as 
they are called, are little more than playthings ; though 
sometimes, as in aphakia, or high myopia, a strong convex 
or concave lens in one of these forms is of use when the 
spectacles constantly worn do not give the vision which 
may occasionally be required. 

The Material of Spectacle Frames is usually gold, 
silver, or steel. Various alloys have also been employed, and 
sold as aluminium or nickel. So far as I have examined 
them, they consist principally of tin, and contain little or 

26 



GENERAL CONSIDERATIONS. 2/ 

none of the metals whose names they borrow. Real nickel 
is too flexible a metal to be used with advantage for spec- 
tacle frames, while, so far, no means have been found of 
soldering aluminium firmly. Were this difficulty overcome, 
the lightness, stiffness, and freedom from rust of aluminium 
would make it an excellent material for cheap frames. 
Silver, like nickel, is too flexible, except for workmen's 
protective goggles, or some such purpose, where very 
heavy frames are allowable. Gold, of from lo to 14 karat, 
is, by far, the best material for frames. Finer than this it is 
too flexible, while if less pure it may blacken the skin. In 
the end, such frames are cheaper than steel, as, owing to 
the liability of the latter metal to rust when in contact with 
the moist skin, the gold will outlast it many times over. 
In eyeglasses, however, the parts are heavier, and the metal 
is not in contact with the skin ; so that there is not the 
same liability to rust. The gold frames furnished by opti- 
cians in this country usually have a stamp mark on the 
inner side of the right temple, near the hinge, which denotes 
the fineness of the gold: thus 8 karat is marked + ; 10 
karat, ^; 12 karat, "^ ; while 14 karat, or finer, is marked 
14k, etc. 

The Component Parts of Spectacles. — A pair of 
spectacles is made up of fifteen or seventeen pieces, whose 
positions are shown in Fig. i. They are : two lenses, two 
eye wires, four end. pieces, two screws, two pins, or dowels, 
two temples, and one bridge. Sometimes the rings upon 
the temples, through which the dowels pass, are formed as 
separate pieces. Fig. 2 shows the name and position of 
each part of an eyeglass. A glance at the more important 
of the many interesting processes required in making these 
different parts will contribute to an understanding of the 
subject. 



28 



SPECTACLES AND EYEGLASSES. 



The Lenses. — The word lens is the Latin name of the 
lentil, a small bean. The resemblance in shape caused the 




Screw holder 



Fig. 2. 



name to be applied to the optical implement. Spectacle 
lenses are usually made of glass ; sometimes of rock 



GENERAL CONSIDERATIONS. 29 

crystal (crystallized quartz). The latter substance has a 
slightly higher index of refraction, so that a lens of a given 
strength may be somewhat lighter when made of it than 
when made of glass. The notion is common that these 
" pebbles," as they are called, possess a peculiar virtue in 
strengthening the eyes or in some other direction. I sup- 
pose the idea is that, being the product of Nature's labora- 
tory, they are necessarily superior. The advantage which 
they may have of being slightly lighter and harder than 
lenses of glass is more than counterbalanced by their 
higher cost, and by the fact that the index of refraction of 
rock crystal is not very constant. 

Of the different kinds of glass, that known as crown 
glass is preferred, on account of the superior brilliancy 
which it possesses. It differs from ordinary sheet glass 
only in the method of blowing. At one point in the pro- 
cess, the mass of glass on the blowpipe assumes the shape 
of a crown; hence the name. Athough glass is theoreti- 
cally a definite chemical compound, the different methods 
of handling make a considerable difference in the product 
of different makers. It consists, chemically, of silicic acid 
united with some two of the metallic bases : sodium, 
potassium, calcium, magnesium, aluminium, iron, and lead, 
but owing to impurities in the glassmaker's raw materials, 
traces of several more of these bases are generally present. 
The bases calcium and sodium are those used for ordinary 
sheet and crown glass ; iron, always present as an impurity, 
giving the product its greenish tinge. To lessen this tint, 
arsenic is employed as a bleaching agent. Peroxid of 
manganese is sometimes used for the same purpose, and it 
is a slight excess of this agent which gives to certain 
samples of glass their pinkish tint. The transparency of 
such glass is thought to be less durable than that having 
the greenish color. 



30 SPECTACLES AND EYEGLASSES. 

The index of refraction of the varieties of glass used in 
spectacle making is as follows : — 

Crown glass, 1.5 

Flint glass, 1.57 

Ordinary sheet glass, 1.53 

Rock crystal, 1.56 

The two broad, polished surfaces of a lens are called its 
refracting surfaces, since it is at these surfaces that the rays 
of light are refracted when the lens is in use. On the shape 
of these surfaces, and their position relative to each other, 
depend all the powers and properties of a lens. Each of 
these surfaces may be either plane, spherical, or cylindrical. 
A spherical surface is such a one as, continued in all direc- 
tions, would form a sphere, and which is, therefore, a seg- 
ment of a sphere. Similarly, a cylindrical surface is the 
segment of a cylinder. Spherical and cylindrical surfaces 
may be either convex or concave. A single surface of a 
lens may be, therefore, either 

Plane, 

Convex spherical, 

Concave spherical. 

Convex cylindrical, 

Concave cylindrical. 
Since every lens has two refracting surfaces, the list of 
lenses which it is possible for the lens maker to produce 
by combinations of these five primary surfaces is as fol- 
lows: — 

1. Prismatic. 

2. Plano-convex spherical. 

3. Plano-concave spherical. 

4. Plano-convex cylindrical. 

5. Plano-concave cylindrical. 

6. Biconvex spherical. 



GENERAL CONSIDERATIONS. 3 1 

7. Biconcave spherical. 

8. Concavo-convex (two varieties) : — 

(a) Radius of curvature of convex surface greater than 
that of concave. (Converging meniscus.) 

(d) Radius of curvature of convex surface less than 
that of concave. (Dispersing meniscus.) 

9. Sphero-cylindrical (four varieties) : — 

(a) Convex sphere combined with convex cylinder. 

(d) '' '' '' '' concave 

(r) Concave " 

{d) '' '' " '' convex 

10. Biconvex cylindrical, axes coincident. 

11. " " *' crossed. 

12. Biconcave ** *' coincident. 

13. '* ** '' crossed. 

14. Concavo-convex cylindrical, axes coincident. 

15. '' '' '' crossed. 
Sections of lenses are shown in Fig. 3, each section 

illustrating two or more lenses, accordingly as we regard 
the curved lines as sections of spheres, or cylinders, and 
the straight lines as planes, or as sections of cylinders in 
the direction of their axes. 

Lastly, the prism may be introduced as an element into 
each of these lenses. Thus we have quite a long list of the 
possible forms of the lens, and that without considering 
the ** toric " surface, which will be spoken of later. Of these 
lenses only the nine first mentioned, and the combination 
of some of them with the prism, are in practical use. The 
others, the bicylindrical lenses, besides being difficult of 
manufacture, have each its optical equivalent in some 
simpler form of lens, either piano-cylindrical or sphero- 
cylindrical. They are only mentioned now because their 
use has been advocated by a few writers in the past. 



32 



SPECTACLES AND EYEGLASSES. 



Difficulties in grinding, and the near equivalence of cer- 
tain of the lenses mentioned among the first nine of our 
list, render the use of some of these lenses quite rare. It 
is, for instance, more difficult to grind a perfect piano- 
spherical lens than it is to grind a bispherical, and as in 
weak lenses, such as are used in spectacles, the action of 




every piano-spherical lens can be nearly exactly duplicated 
by some bispherical one, we seldom find plano-sperical 
lenses in use. Among sphero-cylindrical lenses also it is 
usual to consider certain combinations as equivalent to each 
other. For example, a convex spherical combined with a 
convex cylindrical, as equivalent to some stronger convex 
spherical combined with a concave cylinder. These lenses 
are only strictly equivalent, however, for a small area near 
their optical centers. When their influence on the field of 
vision is taken into account, they can no longer be consid- 
ered identical, as we shall see in considering periscopic 
lenses. 

In Fig. 3, the first three lenses shown act as convergers 
of rays, and are all considered as convex, or '' plus " lenses, 
being designated by the sign +, or sometimes by ex. 
The remaining lenses in the figure act as dispersers of 
the rays and are known as '' minus," or concave lenses, 



GENERAL CONSIDERATIONS. 



33 



and receive the sign — , or sometimes cc. For the terms, 
spherical lens, cylindrical lens, prismatic lens, sphero-cylin- 
drical lens, etc., the words sphere, cylinder, prism, sphero- 
cylinder, etc., are frequently employed and are unobjection- 
able. Finally, the sign o is used for '' combined with " in 
the formula of a combination lens, as -|- 4. sphere + 2. 
cylinder. 

TABLE I. 



1 , 

OLD SYSTEM. i 

1 


NEW SYSTEM. I 


\ I- 


II 


III. 


1 
IV. 


V. 


VI. 


VII. 


VIII. 


No. 








No. 






No. j 


of the 


Focal 


Focal 




of the 


Focal 


Focal 


corres- \ 


' Lens, 


Dfstance 


Distance 


Equiva- ' 


Lens, 


Distance 


Distance 


ponding ofl 


Old 


in English 


in Milli- 


lent in 


■ New 


in Milli- 


in English 


the Old 


System. 


inches. 


meters. 


Dioptries.' 


System. 


meters. 


inches. 


System. 


72 


67.9 


1724 


0.58 


0.25 


4000 


157.48 


166.94 


, 60 


56.6 


1437 


0.695 


0.5 


2000 


78.74 


83.46 


48 


45-3 


1 150 


0.87 


0.75 


1333 


52.5 


5563 


42 


39-6 


1005 


0.90 


I 


1000 


39-37 


41-73 


I 36 


34 


863 


T.16 


1.25 


800 


31-5 


33-39 


30 


28.3 


718 


1-39 


1-5 


666 


26 22 


27.79 


! 24 


22.6 


574 


1.74 


1-75 


571 


22,48 


23.83 


i 20 


18.8 


477 


2.09 


2 


500 


19.69 


20.87 


18 


17 


431 


2.31 


i 2.25 


444 


17.48 


18.53 


16 


15 


^h 


2.6 


1 2.5 


4C0 


15-75 


16.69 


15 


14.1 


358 


2.79 


■ 3 


333 


13-17 


13-9 


14 


13-2 


335 


2.98 


, 3.5 


286 


11.26 


11.94 


13 


12.2 


312 


3.20 


i 4 


250 


9.84 


10.43 


12 


II. 2 


287 


3-48 


■ 4-5 


222 


8.74 


9.26 


II 


10.3 


261 


3.82 


5 


200 


7.87 


8.35 


10 


9.4 


239 


4.18 


5-5 


182 


7.16 


7-6 


9 


8.5 


216 


4.63 


6 


166 


6.54 


6.93 


8 


7-5 


190 


5-25 


i 7 


H3 


5.63 


5.97 


L. 


6.6 


167 


5.96 


8 


125 


4.92 


5.22 


6% 


^•P 


155 


6.42 


9 


III 


4-37 


4.63 


6 


5.6 


142 


7.0 


10 


100 


3.94 


4.17 


5^ 


5.2 


132 


7-57 


II 


91 


3-58 


3-8 


5 


4-7 


119 


8.4 


12 


83 


327 


3.46 


4% 


4.2 


106 


9.4 


i ^3 


77 


3-03 


3.21 


4 , 


3-8 


96 


I0.4 


! 14 


71 


2.8 


2.96 


3% 


3-3 


84 


11.9 


15 


67 


2.64 


2.8 


3li 


3-1 


79 


12.7 


16 


62 


2.44 


2.59 


3 , 


2.8 


71 


14.0 


17 


59 


2.32 


2.46 


2%. 


2.6 


66 


151 


1 ^^ 


55 


2.17 


2.29 


2% 


2.36 


60 


17.7 


1 20 


50 


1.97 


2.09 


^M 


2.1 


53 


18.7 


i 








2 


1.88 


48 


20.94 











The new system of numbering lenses, the dioptric 
system, has so entirely fulfilled the requirements of the 
3 



34 



SPECTACLES AND EYEGLASSES. 



users of lenses, and has so simplified and facilitated our 
every-day work and calculations, that the old or inch sys- 
tem of numbering is rapidly becoming of historical interest 
only. As its use, however, still survives in certain quar- 
ters, and lenses are frequently met with which are marked 
by this system, a table showing the equivalence of the 
ordinary lenses of the test case in the two systems is 
shown on page 33. It is calculated for an index of refrac- 
tion of 1.53. 

The simple apparatus used for grinding a single spherical 
lens is shown in Fig. 4. The disc of glass (a) of which a 
lens is to be made is fastened, by means of pitch, to a small, 
cubical block of iron (^) having a pit in the surface oppo- 
site that to which the glass is fastened. Into this pit fits a 




Fig. 4.— Optician's Lathe for Grinding Spherical Lenses. 

pin (c) upon a lever, which is in the hand of the workman. 
When the free surface of the glass is applied to the surface 



GENERAL CONSIDERATIONS. 35 

of the '' tool " (d) to whose form it is to be ground, it, 
together with the block of iron, turns upon the pin. The 
joints at e and/ allow of lateral and vertical movements of 
the lever, so that the workman is able to carry the glass 
freely over all portions of the tool. 

The tool which gives the shape to the surface of the 
glass is made of steel ; and for spherical glasses is in the 
form of a disc, with its surfaces looking upward and down- 
ward, and revolving about a vertical axis, like a potter's 
wheel. The upper surface of this disc is convex for grind- 
ing concave glasses, or concave for grinding convex 
glasses. Of course, each strength of lens requires a 
separate tool having the requisite convexity or concavity 
of surface. The abrading material placed upon the 
surface of the tool is wet powdered emery of succes- 
sively finer and finer grades until the desired amount of 
glass has been ground away. When this process is com- 
plete, the surface of the glass has the desired spherical 
curvature, but it is rough : that is, it is '' ground glass.'* 
To polish it, a piece of wet broadcloth or felt is smoothly 
applied to the surface of the tool upon which the glass was 
ground, conforming, of course, to that surface. The cloth, 
being sprinkled with wet '' rouge " (a carefully calcined 
sulphate of iron), gives the glass held against it a beautiful 
polish without altering its spherical curvature. The same 
processes must now be gone over with the other surface of 
the lens, after which it is cleaned and cut to a shape 
suitable for its future mounting. 

This is done by means of an implement called a lens- 
cutter, in which the lens rests on a leather cushion and is 
held firmly in position by a rubber-tipped arm, while a 
diamond-tipped glass-cutter, guided by a pattern, traces 



36 SPECTACLES AND EYEGLASSES. 

the oval or other desired outline upon the glass. The 
superfluous glass is removed piecemeal by means of pincers, 
and the lens passes to the next process, which is the 
smoothing and, if necessary, beveling of the edges. This 
is done by hand upon large Scotch grindstones. If the lens 
is to be mounted in a round eyewire, its edge must be 
grooved by means of a file, while a skeleton frame will 
require the drilling of the glass, which may be done by 
hand with a steel drill or by a special machine. 

In grinding a cylindrical lens the surface of the tool is, 
of course, a portion of the surface of a cyHnder, and the 
glass is ground by a to-and-fro motion. It is evident that 
the axis of the cylinder in the future spectacle need not be 
taken into account in grinding, but only in the process of 
cutting to shape for mounting. As a matter of fact, very 
few cylinders are, at present, ground in this country ; the 
glass is brought from Europe with a cylinder already 
ground upon one side and glued to its block of iron for the 
grinding of a spherical or plane surface upon the other. 

When the lenses are of high power it is of advantage 
that they be made in the form of a meniscus, giving what 
are known as periscopic glasses. For instance, if a + 4- 
diopter lens is required, the anterior surface is ground to a 
-j- 6. D. and the posterior surfaces to a — 2. D. It is just 
as advantageous to a cylindrical or sphero-cylindrical glass 
to be periscopic as it is to a spherical, but under present 
methods of grinding it is manifestly impossible to give 
them this form, as the cylinder is ground on one side, and 
the other ground to a plane or sphere, as the case may be. 
Glasses which overcome the difficulty have, however, been 
made, and were described by Dr. George C. Harlan at the 
meeting of the American Ophthalmological Society in 



GENERAL CONSIDERATIONS. 37 

1885, and again in 1889. From the latter communication 
I quote the following description of the glass : — 

'' The lens to which I wish again to call the attention of 
the Society consists of crossed cylinders ground on one 
surface of the glass, the outer being left for any desired 
spherical curve. In this way a meniscus may be produced. 
Here, for instance, is a combination lens giving the effect 
of + 4. O + 2. Cyl. To produce this effect crossed cylin- 
ders of -f 4. and -f 6. are required, supposing the other 
surface of the glass to be left plain. If we wish to give the 
periscopic form to this glass, it can be done by making the 
cylinders 6 and 8, and grinding a — 2. sphere on the other 
side. If a simple cylinder is needed, the spherical curve 
must equal that of the weaker cylinder. 

" I learn from a recent publication by Dr. George J. 
Bull, of Paris, entitled ' Lunettes et Pince-nez,' that glasses 
similar to these have been made Avith more or less success 
before, but have never come into general use. Dr. Bull 
describes them under the name of ' vei'res toriques! The 
tore (Latin fonts) is the surface engendered by a circle 
which turns about an axis situated on the plane of the 
circle. A familiar example of the torus is the circular con- 
vex molding at the base of an architectural column. A 
glass ground upon a wheel having this form will present 
two cylindrical curves at right angles to each other, one 
depending on the radius of the wheel, and the other on the 
radius of the convexity of its rim. It would seem that 
' toric lenses ' is the proper designation of these glasses." 
Fig. 5, A, represents a concave toric lens. In the same 
figure, B is a concave cylindrical lens, introduced for the 
sake of comparison. 

Those who have used these glasses consider them much 
more satisfactory than glasses made by the common 



38 



SPECTACLES AND EYEGLASSES. 



method, and they should be borne in mind when prescrib- 
ing for high astigmatism in patients who use their eyes a 
great deal for work requiring accuracy. 





Fig. 5. 



Eye ^A^ires, Temples, and Bridges. — Eye wires are 
made by wrapping the untempered wire, in the form of a 
spiral, closely about a flattened metal cylinder. Being 
tempered while in this position, the loops of the spiral 
will retain the shape given them. A single cut down 
the side of the cylinder converts each loop into a 
separate oval ring. End pieces and straight temples 
are stamped from sheets of metal, and afterward formed 
and tempered. Hook temples of steel are turned from 
wire upon a lathe. Bridges are usually made of oval or 
half-oval wire, and are simply pressed to the desired shape 
by a forming machine. 

Of the Different Patterns of Spectacles. — In the com- 
mon and strongest form of spectacle, the edge of the glass 



GENERAL CONSIDERATIONS. 



39 



is beveled so as to enter a groove in the wire which sur- 
rounds it. In a second form, in which the edge of the 
glass is grooved for the reception of a fine, round wire, the 
object sought, of rendering the rim of the spectacles less 
conspicuous, is generally defeated by the fact that the glass 
must be made thicker than it otherwise need be, in order to 
give room for the groove on its edge. In concave glasses 
this is not the case, since the edge of the glass is here the 
thickest part, and such glasses may sometimes be mounted 
in this way with advantage. In a third form, called ''frame- 
less " spectacles (Fig. 6), the wire encircling the glass is 




Fig. 6. 



dispensed with altogether, small holes being drilled through 
the glass near its edge for the accommodation of screws 
which fasten the bridge and temples in place. The advan- 
tages of this form are its beauty and inconspicuousness. 



40 SPECTACLES AND EYEGLASSES. 

It should never be prescribed for children, as it is quite 
liable to break at the point where the glass has been 
drilled. The edges of these glasses should not be polished, 
but should be given a dull finish, otherwise they reflect 
the light disagreeably. 

Sides, or temples, have been variously constructed. 
Those having sliding and turn-pin joints are examples of 
antiquated forms. Those now used are the '' hook," or 
''riding-bow," and the plain, ''straight" temple. The 
former are to be preferred in all cases where the glasses 
are to be worn constantly or nearly so, and the latter for 
those who wear glasses for near work only, and require to 
remove them frequently from the eyes. Hook temples are 
made in three lengths, designated as short, medium, and 
long. These are sufficient for all cases. 

Securing a proper fit in the bridge, upon which so much 
of the comfort and efficiency of spectacles depends, was a 
difficult matter until the ingenuity of Dr. Charles Hermon 
Thomas, of this city, suggested what is known as the 
" saddle bridge," which solved the problem. (See Fig. 7.) 
This bridge may be varied to suit every possible case, and 
is always to be preferred. The " K " bridge, formed of 
wires in the shape of the letter K, is allowable in some 
cases. The nearly similar " X " bridge allows the glasses 
to teeter, or see-saw across the nose, with the motions of 
the head. It is, however, the best form of bridge for re- 
versible glasses ; that is, glasses for persons having sight 
in one eye only, who may have their distant glass set in 
one side of a frame and their near glass in the other. By 
using this bridge and straight temples, or hook temples 
without a shoulder at the hinge, the spectacles may be 
turned over so as to bring either lens before the wearer's 
seeing eye. The old-fashioned bridge, called the " curl," is 



GENERAL CONSIDERATIONS. 



41 



unobjectionable for cases in which the bridge of the nose 
is prominent, or for the spectacles of old people, who like 
to slip their glasses down toward the end of the nose. 
None of the forms mentioned, however, have any advan- 
tage over the saddle bridge for any case. A small piece 
of cork is sometimes attached to the under side of the 
bridge where it comes in contact with the skin. It is un- 
necessary if the frames fit the face of the wearer properly. 




Fig. 7. 



K," " Curl," and '* Saddle " Bridges. 



If it be desirable to remove all pressure from the bridge 
of the nose and to transfer it to the sides, it is best done 
by soldering a pair of guards, similar to those used on 
eyeglasses, to the spectacle bridge. 

The earliest spectacles appear to have had round eyes. 
Various other shapes are occasionally seen, as octagon, 
oblong, etc. The oval has about displaced these antiquated 
forms, and is made in sizes known to the trade in America 
as follows : — 

4 



Xo. 


00. 




o. 




I. 




2. 




3- 




4- 
5- 



42 SPECTACLES AND EYEGLASSES. 

TABLE IL— SIZES OF EYES. 

l|| by li in. or 4I by 32 mm. large coq. size. 
I-JI" by ii| in. or 39 by 30 mm. coq. size, 
ly^ by i-i- in. or 37 by 28 mm. standard large eye. 
ii| by 1^ in. or 36 by 25 mm. standard E. G. size. 
i| by I3V in. or 35 by 26 mm. standard interchange. 
^ii by I J in. or 34 by 25 mm. standard small eye. 
I J by ||- in. or 32 by 23 mm. children's size. 

Where glasses are used for near work only, the eyes are 
sometimes made of semi-OYal shape, allowing the line of 
sight to pass over their upper, straight edge when the 
wearer views a distant object. These are known as " half," 
''pulpit," or "clerical" eyes, and are very convenient, 
especially to public speakers, as their name implies. They 
do not seem to me as well known or as generally used as 
they should be. 

When glasses of different focusing power are required 
for distant and near vision, the trouble incident to frequent 
changing is obviated by "bifocal" glasses. That is, the 
lower part of the spectacle eye, which is used for near 
work, is made to differ in focusing power from the upper 
part, which is used for distant vision. Such bifocal glasses 
are also called Franklin glasses, from the philosopher who, 
as we have seen, invented them. 

The object sought may be attained in various ways. In 
the early Franklin glasses each eye contained two half-oval 
pieces, with their straight edges in apposition (a. Fig. 9). 
This has been improved upon by making the line of junc- 
tion a curved one, giving somewhat greater latitude of 
distant vision and rendering the glass more secure in its 
frame. A form of bifocal glasses which were never used to 
any great extent are called " ground " bifocals. They are 
very handsome, containing only one piece of glass in each 



GENERAL CONSIDERATIONS. 



43 









Fig. 8. — Ovals Showing the Actual Sizes of Eyes According to 

Table II. 



44 



SPECTACLES AND EYEGLASSES. 



eye, the upper and lower parts of which are ground of dif- 
ferent Strengths (c, Fig. 9). The mechanical impossibility 
of centering both spherical surfaces upon the same piece of 
glass, however, introduces a prismatic effect which destroys 
their usefulness. The latest and best variety of these glasses 
are called '' cemented bifocals " (d. Fig. 9). They have 
been in occasional use in France for over twenty years, 
though their general manufacture by our opticians is due 






^z> 



o> 



FiG. 9. 



to the efforts of Dr. Geo. M. Gould. To the back, of the 
distance glass is cemented, by means of Canada balsam, 
a small lens whose strength added to that of the distance 
glass equals the strength required for near work. The 
upper edge of the supplemental lens should be ground as 
thin as possible, in order to render it inconspicuous. This 
nearly does away with the objectionable line of junction, the 
spectacles are strong, light, and handsome, and may even 
be made '' frameless," like those represented in Fig. 6, if the 
patient so desire. For cylindrical lenses this form is also 



GENERAL CONSIDERATIONS. 



45 



cheaper, since only the distance glass need have the cylin- 
der ground upon it, the supplemental segment being a 

simple sphere. 

All bifocals have the inconvenience that in walking, the 
floor just in front of the patient's feet is not seen clearly 
because viewed through the near glass. Spectacles which 
revolve on the long axis of the " eye," bringing the distance 
glass to the lower portion of the frame, have been con- 
trived to overcome this difficulty, but they are cumbersome 
and, moreover, it requires more effort to effect the revolution 
of the glass than it does to bend the neck sufficiently to 
bring the upper segment into the line of vision when the 




Fig. io. 



ordinary bifocals are worn. Some persons declare that 
they cannot become accustomed to bifocals however well 
adjusted. Parallel, horizontal lines, as those of a staircase, 
are particularly confusing, it being possible to see each line 
doubled if the junction of the two segments of the glass 
is placed just opposite the pupil. Such persons may prefer 
having an " extra front " (Fig. lo) : that is, a second pair of 
spectacles whose temples are replaced by short hooks, by 
means of which they are hung in front of the frame already 
upon the face. This is a rather clumsy device ; less so, 
however, when the eyes of the extra front are made half 
oval instead of oval. 



46 SPECTACLES AND EYEGLASSES. 

Eyeglasses. — Most that has been said of the varieties 
of spectacle frames apphes as well to eyeglass frames. As 
was mentioned, the chief objection to the latter is that they 
allow a displacement of the axis of a cylindrical or base 
of a prismatic lens. This is a necessary concomitant of 
their being joined by a spring instead of a rigid bridge. 
More or less ingenious frames have been made in which 
the glasses are rigidly joined, and the spring placed in some 
other position (Fig. 11); their weight and cumbersome 
appearance have, however, so far prevented their becoming 
popular. Moreover, the addition of extra parts, which 
must have working room, and the necessarily small amount 
of metal which these parts contain render it extremely 
difficult to construct a really rigid eyeglass frame. So far, 
I have seen none which I consider superior or even equal 
to a carefully fitted frame made in the usual style. 

Another difficulty in the past arose from the fact that 
it was impossible to always place the glass at the proper 
distance from the eye, since the frame must be placed at 
that point where it obtains the best grip upon the sides of 
the nose. This has been in great measure overcome by 
what is called the " offset guard," in which the nose-pieces 
are placed back of the plane of the glasses, instead of in the 
same plane, as formerly. This part is varied in its shape 
so as to adapt it to variously proportioned faces. By the 
use of some one of these variations we are always enabled 
to place the lenses in proper position without removing the 
guards from that position on the nose where they obtain 
the best bearing. When the glasses contain no prism or 
cylinder, or only weak cylinders, a well-adjusted eyeglass 
with '' offset guards " is fairly satisfactory. When made 
frameless, as in Fig. 12, it is the most modern, and certainly 
the most handsome, mounting we have to offer our patients. 



GENERAL CONSIDERATIONS. 



47 



Mtimmi:™^ 




Fig. II.— Forms of Rigid Frame or " Bar Spring" Eyeglasses. 




48 



SPECTACLES AND EYEGLASSES. 




KM 



Fig. 13. — Various Patterns of the Offset Guard. 
" A." P^or shallow bridge, prominent eyes, flat forehead. 
*' B." P"'or shallow bridge, prominent eyes and forehead. 
*' C." The guard used for the average case. 
" D." Deep-set eyes, prominent nose and forehead. 
" E." Same as " C," but for lowering glasses (for reading). 
" F." Same as *' B," but for lowering glasses (for reading). 
" G." Same as " C," but somewhat smaller and neater, although having less 
bearing surface. 

Spectacles for Cosmetic Effect. — Something may 
legitimately be done, at times, in the way of improving the 
appearance of a patient by the application of glasses. The 
blind whose eyes are not only sightless, but unsightly, 
very commonly hide thein behind colored glasses. Neatly 
fitting spectacles with large eyes of ground glass render 
the appearance of such persons less lugubrious. When 
one eye is useless for vision, and at the same time small, 
and the orbit undeveloped, a gratifying improvement in 
the appearance of the patient may be attained by placing 
before the shrunken eye a convex glass of sufficient strength 
to magnify it to the size of its fellow. The condition 
known as epicanthus can generally be removed by wearing 
eyeglasses whose nose pieces draw just enough on the inner 
canthi to smooth out the offending fold of skin. As the 
subjects of epicanthus are generally flat-nosed, it may be 
necessary to furnish the eyeglasses with a pair of hook 
temples to keep them in place. Since operations for this 
disfigurement are so unsatisfactory, such an appliance is 
probably the best treatment we can advise in case the 
trouble is not outp^rown. 



II. THE PRINCIPLES OF SPECTACLE 
FITTING. 

We have now to consider the essential principles of plac- 
ing glasses before the eyes. The usefulness of spectacles 
depends almost as much upon the fidelity with which these 
principles are carried out as it does upon a careful correc- 
tion of the errors of refraction. 

Centering and Decentering. — By the visual axis, or, in 
English, the line of sight, is meant a line from the yellow- 
spot of the retina through the nodal point of the eye to the 
object sighted. 

By the principal axis of a lens we mean a line passing 
through the optical center of the lens (the thickest part, if 
the lens is convex ; the thinnest if concave) at right angles 
to its surfaces. 

The geometrical center of a spectacle glass may be 
shortly said to be that point on its surface which is equally 
distant from the extremities of the figure to which it is cut. 
The principal axis of the lens may or may not pass through 
this latter center. 

We habitually regard as the normal position for glasses 
one in which, when the eyes are looking at a distant ob- 
ject, the visual axes correspond exactly in position with 
the principal axes of the lenses, and together they pass 
through the geometrical centers of the spectacles. In 
other words, the geometrical center of the spectacle eye 
and the optical center of the spectacle lens coincide, and 
the center of the pupil for each eye lies directly behind 

49 



50 SPECTACLES AND EYEGLASSES. 

them. Regarding decentering, some confusion is apt to 
arise because the word is used in two different connections. 
If the visual axis pass to the temporal side of the optical 
center of a glass held before an eye, then, with respect to 
that eye, the glass is said to be '' decentered in." If the 
visual axis pass to the nasal side of the optical center of 
the glass, the latter is '' decentered out." Similarly a glass 
may be decentered in any other direction. When speak- 
ing of spectacles, however, without reference to the eyes 
of the wearer, they are said to be '* decentered in " when 
their optical centers lie to the inner side of their geomet- 
rical centers ; ''decentered out" when the optical centers 




Fig. 14.— Spectacles with Lenses Decentered in. 

G G show the position of the geometrical centers; O O, that of the optical 

centers. 

are to the external side of the geometrical centers, etc. 
A glance at Fig. 14, which represents a pair of spectacles 
decentered in, will make clear what is meant. 

From the above it will readily be seen that when it is 
desired that a patient wear decentered lenses, the effect 
may be obtained in either of the two ways : first, by 
decentering the lenses in their frame ; second, by displac- 
ing them, together with their frames, from what I have 
described as the normal position. The first method has 
the disadvantage of increasing the weight of the glass, 
while the second limits the field of binocular vision. In 



THE PRINCIPLES OF SPECTACLE FITTING. SI 

practice, the second method should be employed to the 
greatest extent possible without unduly interfering with 
binocular vision for the distance at which the spectacles 
will be used, and, should still farther decentering be 
required, the method first mentioned should be brought 
into service. For instance, suppose we wish to order 
glasses with each lens decentered in 8 mm. This would 
mean that the optical centers are to be i6 mm. nearer 
together than the patient's pupils. Let us suppose that by 
a careful consideration of the distance for which the glasses 
are prescribed, of the distance at which they must be 
placed in front of the eyes, and of the size of the spectacle 
eye used, we find that the frame can only be made lo mm. 
narrower than normal without the outer rims of the '' eyes " 
becoming annoying. This leaves 6 mm. to be obtained 
by decentering the glasses in their eye- wires. If the dis- 
tance between the patient's pupils were 60 mm., we would 
order the distance between the geometrical centers of the 
spectacle eyes to be 50 mm., and each eye to be decentered 
in 3 mm. 

Prismatic Effect of Decentering. — It is to obtain a 
prismatic effect from spherical lenses that decentering is 
generally ordered, since a decentered lens is identical with 
a lens of the same strength combined with a prism. This 
is graphically shown by Figs. 15 and 16, the latter of 
which represents a section of a decentered lens, which will 
readily be seen to be precisely the same as the result would 
be if the normally centered lens shown in Fig. 15 were 
split into halves and the prism b a c introduced between 
them. 

The size of the glass disc from which spectacle lenses 
are ground will not allow of more than about 2 mm. of 
lateral decentering for a No. i '' eye ; " 3 mm. for Nos. 2 



52 



SPECTACLES AND EYEGLASSES. 



and 3 ; and 4 mm. for No. 4. Vertically, they may be 
decentered much more. When ordered to decenter later- 
ally more than this, or to furnish a prismatic effect greater 
than can be obtained by this much decentering, the optician 
first manufactures a prism of the requisite strength, and 
then grinds spherical surfaces upon its two faces. It is, 
therefore, of not much importance whether, in ordering a 
sphere prismatic combination, we express the prismatic 
element in degrees of the refracting angle, or in millimeters 
of decentration of the lens : the optician produces the glass 
by whichever method is most convenient. 





Fig. 15. Fig. 16. 

Showing the Prismatic Effect of Decentering. 

The optical center, O, in Fig. 15 coincides with the geometrical center, G, in 
Fig. 16, which represents a decentered lens of the same spherical curva- 
ture ; O has been removed toward the base of the virtual prism b a c. 
{After Maddox.) 



The stronger the lens, the less decentering it requires to 
produce a given prismatic effect, and where the combina- 
tion desired is that of a strong lens with a weak prism, 
the more accurate practice probably is to order the lens 
decentered the requisite number of millimeters. For this 
purpose a table of equivalents, such as is given below, is 
necessary. To use it, we find in the first column the 
strength of the lens used, and on a level with this, in the 
column at whose head stands the strength of the prism re- 
quired, is given in millimeters the amount of decentration 
necessary. 



THE PRINCIPLES OF SPECTACLE FITTING. 



53 



TABLE IIL*— DECENTERING EQUIVALENT TO A GIVEN RE- 
FRACTING ANGLE (INDEX OF REFRACTION, 1.54). 



Lens 


1° 


2° 


3° 


4° 


5° 


6° 


8° 


10° 


I D, 


9.4 


18.8 


28.3 


Zl'l 


47.2 


56.5 


75.8 


95.2 


2 


4.7 


9-4 


14.1 


18.8 


23.6 


28.2 


37.9 


47.6 


3 


3.1 


6.3 


9-4 


12.6 


15-7 


18.8 


25.3 


31.7 


4 


2.3 


4.7 


7.1 


9.4 


11.8 


14.1 


18.9 


23.8 


5 


1.9 


3.8 


5-7 


7-5 


94 


11.3 


15.2 


19. 


6 


1.6 


3.1 


4-7 


6.3 


7-9 


9.4 


12.6 


15-9 


7 


1-3 


2.7 


4. 


5.4 


6.7 


8.1 


10.8 


135 


8 


1.2 


2.3 


3.5 


4.7 


5-9 


7.1 


9.5 


11.9 


9 


I. 


2.1 


3.1 


4.2 


5.2 


6.3 


8.4 


10.5 


10 


•9 


1.9 


2.8 


3.8 


4.7 


5.6 


7.6 


9-5 


II 


•9 


1.7 


2.6 


3-5 


4-3 


5-1 


6.9 


8.7 


12 


.8 


1.6 


2.4 


3.t 


3-9 


4.7 


6.3 


7-9 


13 


•7 


1.4 


2.2 


2.9 


3.6 


4-3 


5-8 


1'Z 


14 


.7 


1.3 


2. 


2.7 


3.4 


4. 


5-4 


6.8 


15 


.6 


1.3 


1.9 


2.5 


3.1 


3.8 


5.1 


6.3 


16 


.6 


1.2 


1.8 


2.4 


3. 


3.5 


4-7 


6. 


17 


.6 


I.I 


1.7 


2.2 


2.8 


3.4 


4.5 


5.6 


18 


•5 


I. 


1.6 


2.1 


2.6 


3.1 


4.2 


5-3 


19 


.5 


I. 


1.5 


2. 


2.5 


3- 


4. 


5. 


20 


•5 


•9 


1.4 


1.9 


2.4 


2.8 


Z-^ 


4.8 



It is one of the beauties of the reformed numbering of 
prisms (see page 85), that by a simple calculation one can 
tell in a moment the amount of decentration required to 
produce any required number of centrads, by means of any 
given lens. 

Divide the number of centrads required by the strength 
of the lens, in diopters. The quotient is the necessary de- 
centration, in centimetei's. For example : to produce a 
prismatic effect of 3. Cr. by means of a lens of 5. D., it is 
necessary to decenter as many centimeters as 5 is contained 
times in 3, which is .8 centimeters. 



* Jackson : " Transactions of the American Ophthalmological Society," 



54 SPECTACLES AND EYEGLASSES. 

Table IV is constructed by applying this rule. In it, 
however, the distances which the lenses must be decentered 
have been reduced to millimeters by moving the decimal 
point one place to the right, in order to make it practically 
more convenient, and render it homologous to Table III, 
like which it is used. 

TABLE IV.— DECENTERING EQUIVALENT TO A GIVEN NUM- 
BER OF CENTRADS. 



Lens 


iCr. 


2Cr. 


3Cr. 


4 Cr. 


5Cr. 


6Cr. 


8Cr. 


10 Cr. 


ID, 


lO. 


20. 


30- 


40. 


50. 


60. 


80. 


100. 


2 


5- 


lO. 


15. 


20. 


25. 


30- 


40. 


50. 


3 


3-3 


6.6 


10. 


133 


16.6 


20. 


26.6 


33-3 


4 


2.5 


5. 


7.5 


10. 


12.2 


15. 


20. 


25. 


5 


2. 


4- 


6. 


8. 


10. 


12. 


16. 


20. 


6 


1.6 


3-3 


5. 


6.6 


8.3 


10. 


^33 


16.6 


7 


1.4 


2.8 


4.2 


5-7 


7.1 


8.2 


11.4 


14.2 


8 


1.2 


2.5 


3.7 


5. 


6.2 


7-5 


10. 


12.5 


9 


I.I 


2.2 


3.3 


4-4 


5.5 


6.6 


8.8 


II I 


lO 


I. 


2. 


3- 


4. 


5. 


6. 


8. 


10. 


II 


•9 


1.9 


2.8 


3-7 


4.6 


5-5 


7-3 


9- 


12 


.8 


1.8 


2.5 


3.3 


4.1 


5. 


6.6 


8.3 


13 


•7 


1.5 


2.3 


3- 


3.8 


4.6 


6.1 


76 


H 


.7 


1.4 


2.1 


2.8 


3.5 


4.2 


5.7 


7-1 


15 


.6 


1.3 


2. 


2.6 


3-3 


4. 


5-3 


6.6 


i6 


.6 


1.2 


1.8 


2.3 


3.1 


3.7 


5. 


6.2 


17 


•5 


I I 


1.7 


2.3 


2.9 


3.5 


4.7 


5.8 


i8 


•5 


I.I 


1.6 


2.2 


2.7 


3-3 


4-4 


5-5 


19 


•5 


I. 


1-5 


2.1 


2.6 


3.1 


4.2 


5.2 


20 


•5 


I. 


1.5 


2. 


2.5 


3. 


4. 


5. 



A cylindrical lens, or the cylindrical element of a sphero- 
cylindrical lens, when decentered in a direction vertical to 
its axis, acts as a spherical lens of the same strength. 
Thus, a + 2. Sph. O + ^- Cyl. axis vertical, decentered 
horizontally, would have the same prismatic effect as a + 3. 
Sph. treated in the same way. As the axis is inclined 
toward the direction of decentration, the prismatic effect of 



THE PRINCIPLES OF SPECTACLE FITTING. 55 

the cylinder diminishes, and disappears when they coin- 
cide. Thus, a +2. Sph. O +i. Cyl. axis horizontal, de- 
centered horizontally, would have merely the prismatic 
effect of a +2. Sph. so treated. 

Normal Lateral Centering. — In proportion as the pris- 
matic effect of decentered lenses is a valuable property 
where this effect is desired, it has to be guarded against in 
those cases which do not require it, to which number 
belong, of course, the great majority of the cases we are 
called upon to treat. If the objects looked at through 
spectacles were always situated in the same direction and 
at the same distance, fixing the position proper for the 
centers would be a simple matter; but, in the movements 
of the eyes, each pupil roves over a territory some 1 8 mm. 
(^ in.) long by 15 mm. broad. When the eyes are directed 
toward a distant object the centers of the pupils are about 
60 mm. apart, and on convergence only 56 mm., so that 
the proper adjustment of spectacles is a series of compro- 
mises between that proper for the position of the eyes in 
which the glasses will be most used and other positions in 
which they will be less used. Of course, the position in 
which they will be most used must receive the greatest 
consideration. 

The proper position for the centers of distance " glasses 
has already been stated. When glasses are to be used for 
near work only, they should be decentered ** in " two or three 
millimeters on each side from this " normal " position, as 
such glasses, being never used in that position, but only 
when the visual axes are converged, would otherwise never 
be rightly centered. What amounts to the same thing, and 
is more often done, is to make the front of the near specta- 
cles four or six millimeters narrower than if they were 
intended for distant vision : four millimeters narrower for a 



56 SPECTACLES AND EYEGLASSES. 

working point of 15 inches; six millimeters narrower for 
one of 10 inches. Concerning the centering of glasses 
which are worn constantly, no rule for all cases can be laid 
down, since accurately centering for any one distance is 
decentering for every other. Fortunately, as a glance at 
Table III w^ill show, it is only with lenses of high power 
that a considerable amount of prismatic effect is developed 
by slight decentering. Where such glasses must be worn 
constantly by a person who spends several hours daily at 
near work, they should certainly be slightly decentered 
inward. 

The distance between the geometrical centers is regulated 
by the size of the spectacle eyes and the width of the space 
between them occupied by the bridge. Where the inter- 
pupillary distance is short, as in children, opticians are apt 
to make the eyes of the spectacles so small as to interfere 
seriously with the field of vision through them. With the 
saddle-bridge there is no difficulty in diminishing the space 
between the spectacle eyes without interfering with the 
form of that part of the bridge which is applied to the 
nose, and the required adjustment should be made in this 
way, leaving the spectacle eyes of good size. 

Normal Vertical Centering. — The glasses require, fur- 
ther, to be so placed that the points where the wearer's 
visual axes penetrate them shall neither be above nor be- 
low the centers. This adjustment is readily seen to depend 
upon the relative height of the bridge of the spectacles and 
the bridge of the nose at the point where the spectacles 
rest. The higher the spectacle bridge, the lower will the 
glasses stand upon the patient's face, and vice versa. 

On the bridge of nearly every nose there may be felt a 
point at which the narrow, upper portion of the nasal bones 
gives place rather suddenly to the broader lower portion. 



THE PRINCIPLES OF SPECTACLE FITTING. 5/ 

Just here, in what has been called the *' natural " position 
(a, Fig. 17), the bridge of the spectacles tends to rest, and 
the attempt to make it remain at any other point will not 
be very successful. In distance spectacles, then, the bridge 
should be made of such height that when resting at this 
natural position, the centers of the spectacle eyes are at the 
same height as the centers of the pupils when the patient 
looks straight forward. When the glasses are to be used 
for near work only, their bridge should be made about 2 
mm., or y^ inch, higher than otherwise, allowing the centers 



Fig. 17. 

to drop that much lower, as the wearer's eyes will nearly 
always be directed to objects below their own level. 

Distance of the Glasses from the Eyes. — As a rule, 
the glasses should be placed just far enough from the eyes 
to escape the lashes in the act of winking. If the lashes 
touch the glass the latter quickly becomes soiled, and to the 
spectacles is, moreover, attributed any falling out of the 
lashes which may occur. Some persons, however, with 
myopia of high degree, prefer the glasses to be placed as 
close to the eyes as possible, regardless of the lashes, be- 
5 



58 



SPECTACLES AND EYEGLASSES. 



cause of the larger clear images which they thus obtain. 
This adjustment of the glasses depends upon the relation of 
the top of the spectacle bridge to the plane of the glasses. 
Where the eyes are deep set, or the nose of the aquiline 
type, the top of the spectacle bridge must be in front of the 
plane of the glasses, or, as it is shortly called, '* out " 
(Fig. 1 8). When the bridge of the nose is low and the 
eyes relatively prominent, as in the negro, Chinese, and 
children, the top of the bridge must be back of the plane 
of the glasses, or ''in," as represented in Fig. 19. 

Perpendicularity of the Plane of the Lenses to the 
Visual Axis. — A very important requirement, and one 





Fig. 19. 



not sufficiently regarded in the fitting of frames, is that the 
plane of the correcting lens when in use shall be as nearly 
as possible perpendicular to the visual axis. The stronger 
the lens the more important is this detail, whose warrant 
lies in the fact that the refractive value of a given lens 
placed obliquely to the visual axis is no longer that indi- 
cated by its number, but is that of some other, stronger 
lens. A cylindrical lens so placed acts simply as a stronger 
cylindrical lens ; a spherical lens, however, as a stronger 
spherical lens combined with a cylindrical lens with its 
axis at right angles to that about which the lens is rotated. 



THE PRINCIPLES OF SPECTACLE FITTING. 



59 



The results of the investigations of himself and others, of 
the effect of the obliquity of a lens to an incident pencil of 
rays, was summarized by Dr. Edward Jackson in a paper 
read before the American Medical Association in 1877, and 
their practical application to this part of our subject pointed 
out. From that communication the following table is 
extracted. It gives in the first column the degrees of 
obliquity at intervals of 5° up to 45^. In the second col- 
umn is shown the refractive value of a I. D. cylindrical, in 
the third that of a I. D. spherical lens so inclined. 

TABLE V. 



Obliquity 


Refractive Power of a 


Sphero-Cylindrical Equivalent 


of 


I D. Cylindrical 


of a I D. Spherical Lens 


the Lens. 


Lens so Placed. 


so Placed. 


0° 


I. D. cyl. 


I. D. spherical. 


5° 


1. 01 " 


1. 00 sph. 3 0.0 1 cyl. 


10° 


1.04 " 


I.oi sph. 3 0.03 cyl. 


15° 


1. 10 " 


1.02 sph. 3 0.08 cyL 


20° 


1. 17 - 


1.04 sph. 3 13 cyl. 


25° 


1.30 " 


1.06 sph. 3 0.24 cyl. 


30° 


1.44 ^' 


1.09 sph. 3 0.36 cyl. 


35° 


1.69 " 


1. 12 sph. 3 0.56 cyl. 


40° 


2.01 " 


1. 16 sph. 30.83 cyl. 


45° 


2.46 " 


1.22 sph. 3 1.24 cyl. 



To fulfil this requirement of perpendicularity to the 
visual axis, the lenses of spectacles used only for distance 
should lie in a vertical plane ; that is, they should face 
directly forward, as shown in Fig. 20. Since the visual 
axes are directed downward and forward when near work is 
done below the level of the eyes, glasses for near must 
face downward and forward, as in Fig. 21, in order that 
the plane in which they lie shall be perpendicular to those 
axes. Furthermore, in viewing near objects the visual axes 
are directed inward and toward each other. This will re- 



6o 



SPECTACLES AND EYEGLASSES. 




Fig. 20. 




Fig. 21. 



THE PRINCIPLES OF SPECTACLE FITTING. 6l 

quire the glasses to face inward also, as represented in Fig. 
22, so that they come to lie in different planes, instead of 
in the same plane, as formerly. 

When " constant " glasses are prescribed, the lenses 
should be placed midway between the proper facing for 
near and that for distance glasses. Then, though the lens 
is not exactly properly inclined either for distant vision or 
near work, the result of such slight obliquity to the visual 
axis is unimportant, since, as a reference to Table V will 
show, it is only in the higher degrees of obliquity that the 
increase in power, and especially the development of 
cylindrical effect from spherical lenses, is rapid. More- 




FlG. 22. 

over, by slightly bending the neck a moderate degree 
of obliquity of the glasses to the visual axes may be re- 
moved without discomfort to the wearer. 

The position of bifocal glasses should also be between 
that proper for near and for distance glasses, but nearer 
that of the stronger glass. This will generally be the near 
glass, as convex bifocals are much more frequently pre- 
scribed than concaves, and such glasses should face only a 
little less downward than glasses intended entirely for near 
work. When concave bifocals are worn, however, they 
should face more forward and much less downward. 

The angle which the plane of the glasses makes with the 
plane of the wearer's face depends entirely upon the angle 



62 SPECTACLES AND EYEGLASSES. 

formed by the plane of the glasses and the temples of their 
containing frames. Thus, when the temples are perpen- 
dicular to the plane of the glasses, as in Fig. 20, the latter 
will face forward and not at all downward. They may be 
made to face downward to any required degree by simply 
turning down the temples at the points where they are 
hinged to the end pieces. These must be equally turned 
down, however, as where only one is turned down, or one 
more so than its fellow, the result is not to make the 
glasses face downward, but to make the glass on the side 
of the lower temple ride higher on the face than its fellow. 
Periscopic Glasses. — In the effort to further apply the 
law requiring that the plane of the lenses shall be perpen- 
dicular to the visual axes, we are met with the fact that 
with biconvex and biconcave lenses this relation is only 
strictly possible within a comparatively limited area sur- 
rounding the optical center of the lens. When the wearer 
looks through the periphery of his glasses the visual axes 
will pierce the lenses obliquely, and the refractive value of 
the latter will, of course, be governed by all the laws of 
tilted lenses. For instance, when the wearer of an ordinary 
convex lens looks through it near the edge, the optical 
effect of the glass before his eye is that of a stronger con- 
vex lens combined with a cylindrical lens ; the axis of the 
latter depending on the part of the periphery pierced by 
the line of sight. In weak lenses, the slight inaccuracy 
of vision produced in this w^ay is of small moment, but 
where the strength of the lens used is greater than about 
2 D. the patient's field of accurate vision is greatly reduced 
in size, and in viewing objects not directly in front of him 
he is obliged to perform wide motions of the head in order 
to be able to see them through the central portion of his 
glasses. This is especially true of cases of aphakia, where, 



THE PRINCIPLES OF SPECTACLE FITTING. 63 

of course, very strong lenses are generally necessary. To 
escape or lessen these disadvantages, strong spherical 
lenses should be, and generally are, made in the form of a 
meniscus, which when placed with its convex surface/r^;;^ 
the eye constitutes a periscopic glass. The ideal of this 
form of lens may be defined as a glass in which the center 
of curvature of one surface coincides with the center of 
rotation of the eye, and that of the other surface approaches 
it as closely as the required strength of the glass will per- 
mit. In such a glass the visual axis will always be perpen- 
dicular to the first surface, and nearly so to the second, at 
whatever point it pierces the glass, and in whatever direc- 
tion the eye may be turned. 

When a cylindrical or sphero-cylindrical lens is required, 
the best form of glass is the toric lens described on page 
37. These lenses have, however, never been manufactured 
extensively, and the process of their manufacture, as well 
as the lens itself, being patented in this country, their cost 
is considerable. By transposing the usual formula, however, 
there may be obtained from any optician a sphero-cylin- 
drical lens which approaches the periscopic form, and is 
certainly superior to one ground after the usual method. 
For illustration, if one desires to order -|- 2. D. Sph. CD -f 
.75 D. Cyl. Ax. 90°, the formula may be transposed and 
the order written for + 2.75 D. Sph. O — .75 D. Cyl. Ax. 
180^. This glass, though optically of the same strength as 
the first, would have an approach to the periscopic form 
if placed with the cylindrical surface next the eye. The 
field of accurate vision would gain in all directions, especi- 
ally in the vertical one, in which diameter, however, its 
enlargement is not of so much consequence as it is later- 
ally. Aphakic eyes offer the best field of usefulness for 
this practice, as in them we have generally to deal with a 



64 SPECTACLES AND EYEGLASSES. 

high hyperopia, and often with hyperopia astigmatism 
requiring for its correction a convex cyHnder with its axis 
horizontal. Let us suppose that after a cataract extraction 
we wished to order + 10. D. Sph. o + 6. D. Cyl. Ax. 180°. 
With this lens, accurate vision would be limited to a vertical 
ov^al field situated directly in front of the patient, beyond 
the confines of which all objects would appear distorted 
by various cylindrical effects. We would, therefore, trans- 
pose the formula into + 16. D. Sph. O — 6. D. Cyl. Ax. 
90°, and this glass will be likely to give the patient much 
more satisfaction than the other would have done, as with 
it he obtains a very good lateral field. 



III. PRESCRIPTION OF FRAMES. 

In order to prescribe the frames for a pair of spectacles, 
we must, after measuring the face or a frame which fits, 
record the dimensions of the frame we desire to order. 
The essential measurements are the intercentral distance, 
or width of front, and the three dimensions of the bridge. 
This list may be extended to include the measurement of 
the angle formed by the bridge and the plane of the lenses, 
that formed by the temples and the plane of the lenses, the 
distance between the temples an inch back of the glasses, 
and the distance from the hinge of the temples to the top 
of the wearer's ear. All these details are, however, so 
ready of adjustment, and the trouble and uncertainty of 
their prescription are so great, that in my judgment they 
are better left until the frame is received from the maker 
and we are ready to adapt it to the patient's face. The 
distance between the centers of the' spectacle eyes is best 
obtained by measuring upon the face the distance between 
the centers of the pupils; the other dimensions of the frame, 
however, are more easily obtained by trying on a sample 
frame and taking the measurements from this, estimating 
any change which may be necessary. To do this requires 
about a half-dozen sample frames whose bridges are of 
different dimensions; also a rule graduated in millimeters, 
or sixteenths of an inch. I have had made for this pur- 
pose a rule which I thinks facilitates the work. As repre- 
sented in Fig. 23, it has upon one side three scales gradu- 
ated in millimeters and conveniently placed for taking the 
6 6; 



66 



SPECTACLES AND EYEGLASSES. 






< 

w 

u 

< 

u 









2 < 





z 









PRESCRIPTION OF FRAMES. 6/ 

different dimensions of the frame, while on the reverse 
side are several ovals showing the principal sizes of spectacle 
eyes. Some of the uses of these scales are shown in Figs. 
24, 25, 30, and 31 ; to avoid confusion one scale only is 
drawn in each diagram. 



Philadelphia^ i8g 

Auime of Pafie7tt, 

R. 

O. D 

O. S 

Unless otherwise specified, furnish the following: Medium length temples; 
saddle bridge; No. 2 eyes. Dimensions are given to middle of wires. Dimen- 
sions given are in millimeters. 

Fraines of^. Catalogue No 

Interpupillary Distance. 

( Height Top 

Bridge X 

i Width of Base 



.M. D. 



A prescription blank such as that here given indicates 
what measurements are required, and will be found useful 
in practice. The upper part is for the lenses, the lower 
part for the frames. 

To Obtain the Interpupillary Distance, with which 
the first dimension of the frame, the distance between the 



68 



SPECTACLES AND EYEGLASSES. 



geometrical centers (a to b, Fig. 24), is generally identical, 
the physician seats himself facing the patient in a good 
light, the latter being directed to look straight before him 



^ . 




=; 


r 




/ 






V= , 


\ > 








^ 


\ / 


\__, Mil lime ler ScaleT"!:^: 


V 


y c 




V 




> 1 



Fig. 24. 

at some distant object. The measuring rule is placed be- 
fore the patient's eyes, as close to them and as far from the 
physician's eyes as possible. The zero of the scale being 
placed opposite the center of one pupil, the center of the 




Fig. 25. 



other may be marked by the physician's thumb nail, as 
represented in Fig. 25, and the distance between them read 
off the scale. This distance seldom varies more than 5mm. 



PRESCRIPTION OF FRAMES. 69 

from 60 mm., or 2^ in. It will be observed that as the 
physician's eyes are less than the length of his arm away 
from the patient's face when this measurement is taken, 
in fact, about two feet away, the marks upon the rule, though 
apparently opposite the pupils, will in reality be a little 
within the centers ; so that the distance obtained will be 
a little less than it should be. When the physician's eyes 
are two feet away from those of the patient, and the rule 
is one inch away from them, the error in measuring an 
interpupillary distance of 60 mm. by this method is almost 




Fig. 26.— Dr. Maddox's 
Pupil Localizer. 




Fig. 27. — The Pupil Localizer 
IN Use. 



exactly 2 mm. This amount should, therefore, be added 
to the apparent interpupillary distance to obtain the true 



one. 



The measurement obtained in this way is sufficiently 
accurate for most purposes, but if a greater degree of accu- 
racy be desired in any case it may be attained by means 
of the little device suggested by Dr. Maddox, which is 
represented in Fig. 26. This is to be placed before one of 
the patient's eyes in an ordinary trial frame having a grad- 
uated bar for showing the distance of each geometrical 
center from the middle of the bridge. The gaze of the 
observed and that of the observing eye being directed to 



70 



SPECTACLES AND EYEGLASSES. 



each other's pupils, the two sights of the implement are 
brought into line between them, as shown in Fig. 27. The 
same procedure is then gone through with for the other 
eye, and the distance of the second pupil from the median 
line of the face, as registered by the trial frame, is added to 




Fig. 28. 



that of the first, to obtain the interpupillary distance. 
This procedure is also of advantage in revealing and meas- 
uring any difference in the distance of the pupils from the 
median line, due to asymmetry of the face. The use of a 
trial frame for making accurate measurements requires the 



PRESCRIPTION OF FRAMES. 7 1 

bestowal of considerable attention to see that the support 
of the nose piece is vertical, the joints close and tight, and 
the markings correct ; otherwise it may readily introduce 
the errors its use is intended to obviate. There are, in the 
shops, many special forms of the ''pupillometer" constructed 
on the principle of a rule held before the eyes and a single 
sight for each pupil. Two of these are shown in Figs. 28 
and 29. The interpupillary distance as registered by them 
requires, of course, the same correction as does that ob- 
tained by the simple graduated rule. 

Height of the Bridge. — This is the distance of the top 
of the bridge above a line joining the centers of the lenses. 
In Fig. 24, it is the distance from e to f, which is the height 




m 1 X T J • t ''\' nf m 



Fig. 29. 

of E above a line joining A and b; not the height of e 
above a line joining c and d, which is sometimes erro- 
neously supposed to represent the height of the bridge. 

If a rule be held horizontally before the patient's eyes, 
with the lower edge touching the nose at the natural posi- 
tion for the spectacle bridge, the height of this edge of the 
rule above the pupil on either side will show at a glance 
about how high the top of the future bridge must be. We 
may then select from our sample frames that one whose 
bridge corresponds most nearly with this supposed height, 
and being sure to place it in the natural position, we care- 
fully note whether the pupils are above or below the 
centers of the eyes of the frame. If they are below these 
centers, sufficient must be added to the height of the bridge 



72 SPECTACLES AND EYEGLASSES. 

now upon the face to allow them to coincide ; if the pupils 
are above the centers, a corresponding subtraction from 
the height of the trial bridge must be made. Each sample 
frame may have its dimensions attached to it, or any frame 
may be used as a fitting frame and afterward measured. 
To measure the height of a bridge the glasses are laid 
upon a sheet of ruled paper, or other object offering a con- 
venient straight line, in such a way that the line passes 
through the geometrical centers of the eyes, or, what is the 
same thing, through the joints of the end pieces on each 



Mil 1 Ime le r Scale. 




Fig. 30. 

side (Fig. 24). The height to which the bridge projects 
above this line is then readily measured. It is seldom 
greater than 10 mm.^ and in rare cases may be a minus 
quantity, the top of the bridge being below the level of the 
centers of the lenses. 

Relation of the Top of the Bridge to the Plane of 
the Lenses. — The measurement required to express this 
relation is that from j to k in Figs. 30 and 3 1 ; not the 
distance of j in front of a line joining c and d, as might 
be supposed. This measurement is also shown at hi. 
Figs. 18 and 19; it is obtained by a procedure similar to 



PRESCRIPTION OF FRAMES. 73 

that just described for obtaining the height of the bridge. 
The rule being placed across the nose at the natural point, 
and the patient requested to wink, it may readily be seen 
whether the lashes touch the edge of the rule. If they do, 
the top of the bridge of the future spectacles must be 
back of the plane of the glasses, or '' in." If they do not, 
we note how much nearer, if any, the edge of the rule 
might be brought without their touching, and so obtain 
a guide to the distance the top of the bridge should be in 




x*a 




Fig. 31. 

front of the plane of the lenses, or '' out." The fitting 
frame which comes nearest to the requirements of the 
case in this particular is then placed upon the face, when 
by viewing it from above or from the side it can quickly 
be seen just how much change, if any, is needed to place 
the glasses a little beyond the reach of the lashes. The 
method of measuring the distance of a bridge in or out is 
so plainly shown in Figs. 30 and 31 that special explana- 
tion is unnecessary. They seldom measure more than 4 
mm. out or 3 mm. in. 

Width of Base. — The measurement from c to d, Fig. 
30, is obtained, like the others, by measuring a bridge which 
fits, or estimating the change necessary in one which does 
not. This dimension is usually from 16 mm. to 20 mm. 



74 , SPECTACLES AND EYEGLASSES. 

This method of obtaining the dimensions of the bridge 
required may seem tedious and uncertain in the description ; 
in use it is not so, and after trial I think will be found 
preferable to any special device so far invented for record- 
ing the measurements. These, after shifting of screws and 
bending of wires, leave one to estimate what changes are 
required just as might have been done without their aid. 
Moreover, the heavy parts and lost space in joints of trial 
frames may readily conceal an error of 2 mm., or even 3 
mm. in some measurements; the large, round eyes with 
heavy rims will not go under the brows, so that the in-out 
measurement of the bridge must frequently be guessed at; 
and the relation of the upper part of the eye wires to the 
brows is not shown. In fact, they introduce, in my estima- 
tion, quite as many sources of error as they eliminate. 

Where the face is unsymmetrical no exact rules of pro- 
.cedure can be given, and considerable ingenuity may be 
required to fit a frame to such a face. If the nose is very 
peculiar, or one side of its bridge markedly steeper than 
the other, it may be of advantage to take an outline of the 
bridge at the natural position by bending a piece of lead 
wire to fit accurately and marking the outline of this upon 
the prescription blank, or sending the wire itself to the 
spectacle maker. Sometimes the brows are overhanging 
and the eyes deep set ; so that the glasses cannot be prop- 
erly centered before the eyes and placed close to them 
without the upper part of the rims burying themselves in 
the brows. In such cases the glasses should be decentered 
upward in their frames and the bridge made sufficiently 
high to bring the optical centers opposite the pupils. 
Though the patient will then look through the upper part 
of his glasses, his field of vision will not be any more limited 
than is already the case because of the overhanging brows. 



PRESCRIPTION OF FRAMES. 75 

Prescription of Eyeglasses. — The dimensions which 
it is usual to furnish in prescribing eyeglass frames are the 
interpupillary distance, of course, with the distance between 
the two upper and the two lower ends of the nose pieces 
when they are in place on the face (a to b, and c to d, 
Fig. 1 2). These measurements alone will not insure a good 
fit in the frames, since neither the contour of the sides of 
the nose to which the guards are applied, the vertical cen- 
tering of the lenses, nor the distance of the latter from the 
eyes are taken into account ; but the same remark applies 
here as to the minor dimensions of spectacle frames, 
namely : that it is more simple, certain, and expeditious for 
the surgeon to make these adjustments in the frames them- 
selves than to prescribe what the manufacturer shall do for 
him. Fortunately, eyeglass frames admit of great variation 
by bending their different parts, and being put together 
with screws, these parts are quickly interchangeable. 
Almost the only thing about them which admits of no 
adjustment is the length of the spring, and it is well for one 
who prescribes many eyeglass frames to have a series of 
such springs at hand from which to replace one which may 
be found too long or too short. 



IV. INSPECTION AND ADJUSTMENT OF 
SPECTACLES AND EYEGLASSES. 

Ordinary prudence demands that the prescriber of glasses 
make a careful examination of the manner in which his 
directions have been carried out, since neglect of this pre- 
caution may nullify the results of the most painstaking 
correction of the refraction. If the surgeon himself furnish 
the spectacles, it is doubly incumbent on him to make a 
thorough inspection of glass and frame, and to carefully 
adjust the latter so as to be entirely comfortable to the 
wearer. Then, too, it is not enough that the frames cor- 
rectly perform their function at first ; they must continue 
to do so. Should there be no optician in his neighbor- 
hood, the surgeon will be called upon to bring to a proper 
shape frames which have passed through all sorts of acci- 
dents, and it is better that he should do this work than 
entrust it to less competent hands. 

Proving the Strength of Lenses. — The focal length of 
a convex lens may be directly measured by finding the 
distance at which it brings the sun's rays to a focus. To 
do this, the rays which have passed through the lens are 
simply caught upon a piece of paper or other screen, the 
two being held in such relationship that the image of the 
sun formed on the screen is round. The screen is then to 
be moved back and forth until the point is found at which 
this image is smallest, and the distance of such point from 
the lens is the focal length of the lens. To learn the 
strength of the lens in diopters, we divide lOO centimeters 

76 



INSPECTION AND ADJUSTMENT OF SPECTACLES. "J^J 

(one meter) by the focal length expressed in centimeters, 
or 40 inches (about one meter) by the focal length expressed 
in inches. For instance, if we found the focus of the lens 
under examination to be distant 10 in., or 25 cm., from the 
lens, 40 in. divided by 10 in., or 100 cm. divided by 25 
cm., will alike give a quotient of 4, and the lens measured 
was, therefore, a +4. D. 

The focal length of a concave lens may be similarly meas- 
ured by combining it with a stronger convex lens and then 
measuring the strength of the resulting weaker convex. 
The strength of the original convex used being known, we 
have only to subtract from it the weak convex resultant to 
find the strength of the concave with which we are dealing. 
The focal length of convex and concave cylindrical 
lenses maybe measured in the same way as the correspond- 
ing sphericals, it being only necessary to observe that the 
parallel rays of light after passing through a convex 
cylindrical lens are arranged in the form of a line at the 
focus of such lens; not brought to a point, as is the case 
with convex sphericals. 

Phacomcters. — Such methods as the one described 
above are, however, too tedious for ordinary use, though 
quite elaborate contrivances called phacometers have been 
devised on this principle. K lens measure constructed on 
an entirely different idea has lately appeared, the invention 
of Mr. J. T. Brayton, of Chicago. Fig. 32 shows the size 
and appearance of the instrument, as well as the method of 
its use. Of the three steel pins which project from its top 
the two outer ones are fixed, while the central one moves 
up and down easily but is held up by a spring. On press- 
ing the surface of a spherical lens squarely against these 
points, the central one will be depressed until they all 
three touch the glass, the curvature of the surface of the 



78 



SPECTACLES AND EYEGLASSES. 



lens determining the amount of such depression. The 
motion being transferred through a rather simple mechan- 
ism to the hand upon the dial, this travels over a scale 
which shows in diopters and in inches the strength of the 
lens corresponding to the surface tested. The other sur- 
face is then to be explored in the same way. If the lens is 
biconvex or biconcave, the results of measuring each sur- 



^pj. FEB/24 /5Q, 

c/iCAGO. J 




Fig. 32. 



face separately are added together; if periscopic, the less is 
deducted from the greater. When used upon a cylindrical 
surface the hand will stand at zero when the three points 
are in line with the axis of the cylinder. When the points 
are placed at right angles to the axis the strength of the 
cylinder is shown. 

Since this instrument indicates the refractive value of a 
lens from the curvature of its surfaces only, leaving out of 



INSPECTION AND ADJUSTMENT OF SPECTACLES. 79 

account the index of refraction of the material, it is evident 
that it can be accurate for only one variety of glass. As 
found in the shops it is adjusted for crown glass, and for 
lenses of this material it is quite accurate ; while its con- 
venience and low price as compared with other phacom- 
eters recommend it to favor. 

Neutralization of Spherical Lenses. — The method of 
determining the strength of spectacles which is of most 
general utility is the well-known one of neutralization. If 
a convex spherical lens be held about a foot from the eye, 
and any object, say that part of a window frame where a 
vertical and horizontal line cross, be viewed through it, any 
motion given the lens will result in an apparent motion in 
the opposite direction of the object sighted. That is: if 
the lens is moved to the right, the object appears to move 
to the left ; if the lens is raised, the object appears to sink. 
If the same maneuver be employed with a concave spherical 
glass, the object again appears to move, but this time in the 
same direction as the motion imparted to the lens ; if the 
lens is moved to the right, the object appears to move to 
the right also. Here we have the readiest possible means 
of distinguishing between a convex and a concave lens. 
Moreover, one gets in this way an idea of the strength of a 
lens, as the stronger the lens the more rapid is the apparent 
motion of the object seen through it. 

If, continuing the experiment, the two lenses be placed 
together, with their curved surfaces in apposition, and a 
trial be made of the effect of moving them before an object, 
as was done previously with each lens singly, the object 
will appear : i (if the concave lens is the stronger), to move 
in the same direction as the motion of the glass, but more 
slowly than before ; 2 (if the convex lens is the stronger), 
to move in the opposite direction to the motion of the 



8o 



SPECTACLES AND EYEGLASSES. 



glass, but more slowly than before ; 3 (if the lenses are of 
equal strength), to have no motion. Therefore, to find the 
strength of a spherical lens it is only necessary to combine 
it in this way with successive lenses of known strength and 
of the opposite sign until that one is found which neutral- 
izes the apparent motion of objects seen through it. This 
lens is the measure of the strength of the one tested. This 
method is accurate within an eighth diopter, or less, for 
plano-convex and planoconcave lenses; with bi-convex 
and bi-concave glasses it is only possible to neutralize the 





Fig. 33. 



Fig. 34. 



apparent motion near the center of the lens ; toward the 
edges motion will still be visible when the lenses are 
strong. 

Cylindrical lenses may be recognized by viewing through 
them some object presenting a straight line, say the vertical 
line of a window sash. If the cylindrical lens be rotated 
about the visual axis, the portion of the vertical line seen 
through the glass will appear to be oblique, as compared 
w^ith that seen above and below the glass (Fig. 33). This 
oblique displacement takes place in a direction contrary to 



INSPECTION AND ADJUSTMENT OF SPECTACLES. 8 1 

the rotary motion given the lens if the latter is convex, and 
in the same direction as the motion if the lens is concave. 
To ascertain the position of the axis of a cylindrical lens it 
should be rotated slowly in this manner until the line seen 
through it appears continuous with that above and below 
(Fig. 34). This line will then lie either in the axis or at 
ricfht aneles to it. To ascertain which of the latter is the 
case, the effect of motion from side to side is to be tried. 
If the axis of the cylinder corresponds with the vertical 
line looked at, motion from side to side produces apparent 
motion of the object; if, however, the axis lies at right 
angles to the vertical line no such motion results. In other 
words, in the direction of its axis a cylindrical lens acts as 
a piece of plain glass ; across its axis it acts as a spherical 
lens of the same strength. If it is desired to know upon 
which surface of a lens the cylinder is ground, this may be 
ascertained by holding the lens nearly horizontally betw^een 
the eye and a window, so that the line of sight strikes its 
upper surface very obliquely. One can thereby see the 
lines of the window reflected upon the upper surface of the 
lens. By rotating the lens about its optic axis these lines 
appear broken if the surface is cylindrical, but retain their 
continuity if the reflecting surface is spherical. The direc- 
tion of the axis of a cylindrical lens having been ascer- 
tained, its strength may be determined by neutralizing it 
with a cylinder of the opposite sign, as was explained when 
speaking of spherical lenses. Care must be taken that the 
two lenses are so placed that their axes coincide. 

A Sphero-Cylindrical Lens is equal in refractive effect 
to two cylindrical lenses with their axes perpendicular to 
each other. Having found that axis across which motion 
is least rapid, we may neutralize the motion with a spheri- 
cal lens and, holding these two together, proceed to neu- 
7 



82 SPECTACLES AND EYEGLASSES. 

tralize the motion across the other axis just as if dealing 
with a simple cylinder. When our object is not to deter- 
mine the strength of an unknown lens, but to see if the 
lenses of a pair of spectacles agree with the prescription 
previously written, we may, of course, shorten the above 
procedures by picking out from the test case the glass, or 
glasses, which will neutralize the spectacles if the latter 
are of the proper strength, and observing whether the 
apparent motion of objects ceases when they are held 
together. 

Locating the Optical Center. — Every glass before be- 
ing worn should be examined with regard to the position 
of the optical center of each lens and the distance of 
these from each other, as inaccuracy in this important par- 
ticular is not uncommon. Indeed, in the cheap spectacles 
which some persons unfortunately buy, proper centering is 
the exception. In grinding large numbers of lenses by 
machinery a certain number in each batch are, I believe, 
always found to be badly centered. These are not returned 
to the wheel or the furnace by the thrifty manufacturer, but 
are graded as second class, or if very bad indeed as third 
class, and v/ith those which will not pass inspection in other 
particulars go to make up the trash sold by peddlers. 

A simple way to find the location of the optical center is 
to hold the lens about a foot above the corner of a rectan- 
gular card lying on the table. The corner seen through 
the lens will only appear complete and continuous with the 
rest of the card when its tip is opposite the optical center. 

In Fig. 35, A represents a lens so held that its optical 
center is marked by the corner of the underlying card; b 
is a lens improperly held. The center first found may be 
marked with a speck of ink, the center of the other spec- 
tacle glass found in the same way, and the distance between 



INSPECTION AND ADJUSTMENT OF SPECTACLES. 



83 



them measured. If care is taken to hold the glass exactly 
level and the eye directly over it this method will give 
results accurate enough for most purposes. 




Fig. 35. 

The Apex of a Prism may be determined by viewing 
through the glass fine lines crossed at right angles, holding 
the prism so that its edge and supposed apex just touches 
one line at the point of intersection. When the real apex 





Fig. 36. Fig. 37. 

Method of Finding the Apex of a Prism. [After Aladdox.) 

of the prism coincides with the intersection of the lines, the 
appearance presented is that shown in Fig. 36 ; when, how- 
ever, the apex is to one side of the point of intersection, 
the line seen through the prism appears broken, as in Fig. 
37. In this case the prism is to be rotated until the line 
appears continuous, when the point of intersection of the 
lines will mark the apex of the prism. 



84 SPECTACLES AND EYEGLASSES. 

The Strength of a Prism may be expressed in two 
ways ; either in degrees of the refracting angle, which is 
the angle forming the edge and separating the two refract- 
ing surfaces of the prism, or by means of some formula 
which denotes the power of the prism to turn a ray of light 
from its course. This power is usually expressed in degrees 
of the angle of deviation, which is the angle separating the 
course of a ray of light after having passed through the 
prism from that which it would have pursued had its course 
been unobstructed. The obvious advantage of the latter 
mode of expression, which gives directly the optical 
strength of the prism, over the former, which merely states 
the value of a physical angle from w^hich the strength can 
be more or less accurately inferred, has called forth several 
suggestions for an improved method of numbering ophthal- 
mological prisms. Dr. Edward Jackson was the first to 
point out that the prism had escaped attention when the 
numeration of our other glasses was reformed. He pro- 
posed that in harmony with the mode of stating the value 
of angles which is commonly accepted in other depart- 
ments of science, they be marked in degrees of their 
angles of deviation. With the idea of conforming their 
numeration to the dioptric system of numbering lenses, 
Mr. C. F. Prentice proposed to adopt as a unit that prism 
having the power necessary to produce one centimeter of 
deviation in the course of the ray after having passed 
through and the distance of one meter beyond the prism. 
Dr. S. M. Burnett proposes that this unit be called the 
prism diopter, and that the centimeter of deviation be 
measured upon a plane surface — that is, upon a tangent of 
the arc whose radius is one meter. 

Within practical limits the objections which have been 
raised to the prism-diopter are few and of little moment, 



INSPECTION AND ADJUSTMENT OF SPECTACLES. 85 

and it has great simplicity to recommend it. In a series 
of prisms so numbered, however, the higher prisms are not 
simple multiples of the lower ones. Twenty prisms of two 
P. D. each would not be equal to a prism of 40 P. D., but 
to a prism of 42 P. D. 

The coitrad as a unit of measurement of prism power 
was suggested by Dr. W. S. Dennett. After mature con- 
sideration this unit has been formally recommended by the 
American Ophthalmological Society, and will doubtless in 
a few years entirely, as it has already to a great degree 
displace the old system of numbering. 

The term radian denotes in mathematics a portion of the 
arc equal to the radius. The centradian is the one hun- 
dredth part of the radian. The centrad is such a prism as, 
held with one surface perpendicular to the incident ray, 
causes a deflection equal to a centradian. If the measure- 
ment be made at one meter, then, the radius and radian 
being each one meter long, the centradian will equal a 
centimeter, measured on the arc, and the centrad is such a 
prism as will produce this amount of deflection. If the 
measurement be made at two meters — a very convenient 
distance — one centrad will produce a deflection of one 
hundredth of two meters, or two centimeters. 

It will be seen that the practical difference between a 
centrad and a prism-diopter consists in this, that in the 
former the amount of deflection is measured on the arc, 
while in the latter it is measured on the tangent. For 
ophthalmological prisms, w^hich are of necessity w^eak, the 
difference between centrads and prism-diopters is so slight 
as to be of no moment. The numeration of prisms by 
centrads has the advantage that it is founded on a method 
of stating the value of the angle which is used in other 
departments of physics. Its higher numbers in the scale 
are, moreover, simple multiples of the unit. 



86 



SPECTACLES AND EYEGLASSES. 



Over the system of numbering prisms in degrees of the 
refracting angle the use of the centrad has all the advan- 
tages possessed by the modern numeration of spherical 
lenses over the old. Its use, moreover, involves no per- 
plexity in the mind of one who has become habituated to 
the former method, since, as shown in Table VI, the dififer- 



TABLE VL— SHOWING THE EQUIVALENCE OF CENTRADS IN 
PRISM-DIOPTERS AND IN DEGREES OF THE REFRACT- 
ING ANGLE (INDEX OF REFRACTION 1.54). 



Centr 


ADS. Prism Diopters. 


Refracting Angle. 


I 


I. 


i°.oo 


2 


2.0001 


2°. 12 


3 


30013 


3°.i8 


4 


4.0028 


4°.23 


5 


5 -0045 


5°.28 


6 


6.0063 


60.32 


7 


7.01 15 


7°-35 


8 


8.0172 


8^.38 


9 


9.0244 


9°-39 


10 


10.033 


io°.39 


II 


1 1 .044 


i^'^'Sy 


12 


12.057 


i2°.34 


13 


130 4 


I3°.29 


H 


14.092 


I4°.23 


15 


15114 


I5°.i6 


16 


16.138 


i6°.o8 


17 


17.164 


16^.98 


18 


18.196 


17^.85 


19 


19230 


i8°.68 


20 


20.270 


19° 45 


25 


25-55 


23° 43 


30 


30.934 


26°.8i 


35 


36.50 


29^.72 


40 


42.28 


32°. 1 8 


45 


48.30 


34°.20 


50 


54.514 


35°-94 


60 


68.43 


3^°-3i 


70 


84.22 


39°.73 


80 


102.96 


40°. 29 j 


90 


126.01 


40°.49 


100 


155-75 


39°.i4 



INSPECTION AND ADJUSTMENT OF SPECTACLES. 87 

ence in value of one of the old and one of the new prisms 
of the same number is slight for the weaker, more used 
prisms. The one, however, represents a definite, fixed 
value; the other does not. 

As the surgeon has a choice of two essentially different 
methods of numbering, so, also, he has at his command 
several modes of determining the strength of unknown 
prisms, and may select that one which is simplest and 
involves least calculation for the numeration which he 
uses. The refracting angle may be readily found by 
means of Table III, introduced when speaking of the pris- 
matic equivalent of decentered lenses. The situation of 
the optical center is to be marked upon a spherical lens of 
convenient strength, and the prism to be tested super- 
imposed. By viewing the corner of a card through these 
two glasses, as was directed in describing the method of 
finding the optical center, this center will be found to have 
been carried toward the base of the prism. The position 
of this apparent optical center is to be likewise marked 
upon the spherical lens, and its distance from the true one 
measured. In the left-hand column of Table III find the 
strength of the lens used, and on a level with this across 
the page the distance in millimeters between the true and 
apparent optical centers. At the head of the column in 
which this measurement is found will stand the strength of 
the prism with which the lens was combined, this strength 
being expressed in degrees of the refracting angle. For 
instance, if having combined an unknown prism with a + 
7. D. lens we find the apparent displacement of the optical 
center to be 4 mm., the table shows at a glance that the 
refracting angle of the prism tested had a value of 3^. 

The refracting angle may be directly measured by 
adapting the legs of a pair of compasses to the two re- 



88 



SPECTACLES AND EYEGLASSES. 



fracting surfaces and then laying the compasses on an 
ordinary protractor. Various other mechanical contriv- 
ances have been invented for effecting the same purpose, 
one of the best of which is represented in Fig. 38. It con- 
sists of a bed-plate A, upon the front of which is affixed a 
degree-circle G, and hinged to A at H is the upper plate B 




m M 



Fig. 38. 



held up by the spring M, not plainly shown because it is 
under B. The upright face-plate C stands at right angles 
to B. On top of C is the degree-circle E. The index 
finger F with the lower part D D' is made of steel and 
pivoted at P to swing easily over any portion of the dial 
plate. In measuring a prism, the position of the index 
finger F will be governed by the difference of the thick- 



INSPECTION AND ADJUSTMENT OF SPECTACLES. 89 

ness of the lens at the points D and D^ and the degrees of 
the refracting angle of the prism will be indicated on the 
scale E by the pointer F. 

The surgeon is, however, very little concerned with the 
refracting angles of prisms, except as they are the basis of 
the old system of numbering, which will doubtless soon be 
superseded by one in which the number of the prism shall 
express in centrads the power which that prism possesses 
of causing deviation in a ray of light. One of the simplest 
and most convenient devices for measuring this power is 
that suggested by Dr. Maddox. It consists of a strip of 
cardboard suspended horizontally on the wall on a level 
with the eyes of the observer. The upper border of the 




card (Fig. 39) is marked from right to left with a scale of 
degrees, or rather tangents of degrees, proper to the distance 
at which the prism is to be held from the card. In Table 
VII is given the distance from the right-hand border of the 
card of the mark for each degree of deviating angle. With 
the help of this table one may readily construct the scale, 
using column A if he elect to work at 6 feet, or column B 
if a 2-meter range be preferred. 

To practice this method of prismetry, the glass to be 
tested is held at the proper distance from the card, its apex 
to the left, and its upper border just below the figures of the 
scale, as in Fig. 39. The observer's eye being placed behind 
the prism, the right vertical border of the card appears dis- 



90 



SPECTACLES AND EYEGLASSES. 



placed toward the observer's left and points upward to the 
number expressing the strength of the prism in degrees of 
the angle of deviation. During this maneuver care must 
be taken that the prism is held at precisely the distance 
from the card for which the scale of the latter is arranged ; 
also that the apex of the prism points exactly to the left. 
This latter requirement may be secured by rotating the 
prism until the line of the bottom of the card appears un- 



TABLE VIL^ 



Foe Marking a Card in Tangents of Degrees at 6 Feet 




(Column A) ; or 2 Meters (Column B). 




A 


B 




A 


B 


1° 


1.25 in. 


349 cm. 


9° 


II. 4 in. 


31.29 cm. 


2° 


2.5 '' 


6.98 " 


10° 


12.6 '* 


34-73 " 


3° 


Z'1 '' 


10.467 " 


11° 


14.0 " 


38.16 " 


4° 


5.0 " 


13-95 " 


12° 


15.3 " 


41.58 " 


5° 


6.Z " 


17.43 " 


13° 


16.6 " 


44.99 " 


6° 


7-57 " 


20.9 " 


14° 


17.9 " 


48.38 " 


7° 


8.84 *' 


24-37 " 


15° 


19.3 - 


51.76 " 


8° 


10.12 " 


27.83 - 


16° 


20.64 " 


55.13 " 



broken, as at a, in Fig. 39. In adapting this method of 
prismetryto centrads or prism diopters, the scale at the top 
of the card should simply be laid off in centimeters, and 
the prism be held at the distance of one meter. Each cen- 
timeter that the right border of the card is. apparently 
moved to the left, on viewing it through the prism, will 
then represent one centrad, or one prism diopter. 

Scratches, Specks, Bubbles, Flaws, etc., in the glass 
will hardly escape detection if they are carefully looked for 

^ Yrom Maddox: *' The Clinical Use of Prisms." 



INSPECTION AND ADJUSTMENT OF SPECTACLES. 9 1 

while the lens is held in different lights. Placing the glass 
against a dark background and allowing a bright light to 
fall obliquely upon it will perhaps bring them out as plainly 
as any other maneuver. 

Irregularity of the Surface may be discovered by re- 
flecting from that surface any object having regular out- 
lines. The observer should stand facing a window, hold- 
ing the lens against a dark background in his left hand, 
and pass a straight-edged piece of paper held in his right 
hand betw^een his eyes and the lens. Two images of the 
paper will be reflected from the lens, — one formed by each 
surface. Any irregularity of these surfaces will make the 
images appear broken, or with wavy outlines. 



Fig. 40. 

Adjusting Spectacle Frames. — It requires some little 
practice to enable one to tell at a glance just where such 
an irregularly shaped object as a spectacle frame has been 
wrongly bent; having found the error, it is a more simple 
matter to correct it. For the latter purpose two small 
pliers are required. They should have narrow but strong 
jaws, round in one pair and square in the other. As 
found in the shops, the grasping surfaces of the jaws are 
generally roughened, but should be smoothed off with a 
file, lest they scar the gold when in use. A small, stout 
screw-driver w^ith a point suited to the screws of spectacles 
will also be necessary. 



92 



SPECTACLES AND EYEGLASSES. 



Eye-wires are generally of such light material as to take 
their shape from the contained glass, and are, therefore, not 
liable to become misshapen. Sometimes the long axis of an 
oval eye gets rotated within the eye-wire (Fig. 40), so that 
it no longer stands squarely across the face. By loosening 
the screw it can readily be re-adjusted. Abnormal crooked- 




FiG. 41. 



ness about the bridge is best disclosed by placing a straight 
edge (indicated by the line S E in Figs. 40, 41, 43, 44, and 
45) in such a position as to enable one to compare the two 




Fig. 42. 

sides of the frame. If the bridge is bent at its junction 
with the eye-wire a rotation results, looking very much 
like that just mentioned, but dependent upon an entirely 
different fault (Fig. 41). It is readily corrected with pliers 
or fingers. 



INSPECTION AND ADJUSTMENT OF SPECTACLES. 93 



\^ 




Fig. 43. 




Fig. 44. 




Fig. 45. 



94 SPECTACLES AND EYEGLASSES. 

The planes of the glasses may cross each other (Fig. 42), 
in consequence of a twist in almost any part of the bridge, 
though the trouble is, usually, that the angle of the bridge 
at A is not of the same size as its fellow of the opposite 
side. The bridge is inclined, as shown in the cut, more to 
one glass than to the other. It requires application to the 
patient's face to determine which is the proper inclination, 
and in order that the glasses may be equalized at this and 
not at the improper one. 

In Fig. 43 the bend is at the junction of the eye-wire 
with the bridge, rendering corresponding angles of the two 
sides of the frame unequal. The diagram shows the 
change necessary to correct the trouble. A similar fault 
is shown in Fig. 44. This appears at first sight to be just 
like the last ; it is, however, a neighboring angle of the 
bridge which needs equalizing with its fellow. 

In the frame represented in Fig. 45 the glasses lie in the 
same plane, but one of them is nearer the center of the 
bridge than the other, due to the fact that, of the angles 
of the bridge which can be seen by viewing the frame in 
this position, the two which lie on one side of the curved 
portion are too much open, while the two on the other side 
are too little so. Of course, the bridge may be misshapen 
in any portion of its extent, but the illustrations given are 
sufficient to show the sort of faults one may expect. 

Having rectified all want of symmetry in the " front," 
the defects in the fit of the temples can best be corrected 
by trying the frames on the patient's face. If on doing so 
it is found that their temples cut into the temples of the 
wearer, instead of just touching the skin, as they should do, 
the trouble is obviously that the distance between the tem- 
ples is too small, and they must be bent out at the hinges, 
so as to throw them, when open, further apart. This is 



INSPECTION AND ADJUSTMENT OF SPECTACLES. 95 

done with the square-jawed pliers, seizing the wire close 
up to the hinge. When the opposite condition pertains? 
that is, when the distance between the temples is too great, 
leaving a space between each wire and the side of the 
wearer's head, they require to be bent in. To do this, take 
the end of each side in turn in the square-jawed pliers, in 
such a way that the edge of one jaw shall be in contact with 
the temple as close to the hinge as possible and the latter 
be held rigidly open. The temple may then be pressed in 
with the fingers, and will bend at the point where it is pressed 
against the edge of the pliers. If the latter are rightly 
placed this does not make an angle in the wire forming the 
temple, but simply alters the angle already formed at a in 
Fig. 45, by the expansion of the end of the temple to help 
form the hinge. Care must be taken that one temple is 
not bent out more than the other, or, as is apt to be the 
case, become so during use. When this happens the 
effect is quite different from what might be expected. The 
glass on the same side as the temple the more bent out 
will be brought closer to the eye, while its fellow will be 
carried further forward and the bridge will ride obliquely 
across the nose. To remedy this it is only necessary to 
equalize the divergence of the temples. 

The curve of hook temples given them by the maker 
will rarely be found to fit comfortably behind the ear. As 
has been pointed out by Dr. Charles H. Thomas, the proper 
form for hook temples is a straight line from the hinge to 
the top of the ear, where a sharp curve should join this part 
of the temple to the easy curve which corresponds to the 
back of the ear (Fig. 42). Where the curve given the hook 
is too wide and is extended upon that part of the wire rest- 
ing against the patient's temple, as shown by the dotted 
line in Fig. 46, there is a constant tendency of the specta- 



96 SPECTACLES AND EYEGLASSES. 

cles to slide forward. The wire, moreover, touches the 
back of the ear for a short distance only, where its pressure 
is further increased by the fact of the whole temple being 
put upon the stretch and acting as a spring. Especially at 
first should the frames not fit too tightly, as the skin is then 
more easily irritated by the wire than when it becomes 
accustomed to its presence. 

In persons whose ears stand out far from the head a 
certain ridge upon the cartilage of the ear is thrown into 
prominence. Since the curve of a hook temple is a regular 
one, it will rest upon this ridge and be very uncomfortable ; 
indeed, it may cut through the skin and into the cartilage. 



X \ 




Fig. 46. 

Under such circumstances the portion of the wire which is 
behind the ear should be made to follow every depression 
and elevation of the surface with which it is in contact ; as 
it should in any case where the auricle is deformed or 
irregular in any way. 

If one lens stands higher upon the face than the other, 
so that the patient looks through the upper part of one 
glass and the lower part of the other, it will be found that 
the temple on the side which stands the higher is turned 
down more than its fellow. It should be raised, or more 
frequently its fellow should be lowered. The fault may 
lie in the bridge, as shown in Fig. 42, or in the end piece, 
or in the temple itself In the first instance, bringing the 



INSPECTION AND ADJUSTMENT OF SPECTACLES. 97 

lenses into the same plane removes the difificulty; in the 
second, take the end piece in the round-jawed pliers, the 
jaws being applied to its edges close up to the eye-wire. 
Holding these pliers in the left hand, apply the square 
jaws of the other pliers to the surfaces of the end piece ; 
when, by twisting the latter about its long axis, the temple 
may be turned down to any desired extent. Thus, the 
temple is not bent at all, but the end piece between the 
hinge and the eye-wire. Nearly the same effect may be 
produced by bending the wire of the temple close up to the 
hinge. As was remarked before, in speaking of the facing 




Fig. 47. 

of the glasses, the effect of turning down both temples is 
not to make both lenses stand higher upon the face, but to 
make the glasses face more downward. 

Sometimes when the glasses do not sit properly the 
trouble will be found to be not in the frames but in the 
wearer. A considerable amount of asymmetry of the two 
sides of the face is not uncommon. One ear or one eye 
may be higher than its fellow, either of which conditions 
will make the glasses seem awry, and render necessary a 
compensating asymmetry of their frames. 

Adjustment of Eyeglasses. — The starting-point in 
adjusting eye-glasses is at the nose pieces, whose free sur- 



98 



SPECTACLES AND EYEGLASSES. 



faces should be made to conform accurately to the bones of 
the nose by which they are supported. When received 
from the maker they are generally curved, presenting a 
convexity toward the nose. As the bones of the sides of 
the nose at the point where the guards are to rest are 
usually more or less convex also, the bearing obtained is 
a most insecure and uncomfortable one, as a glance at Fig. 
47 will show. In Fig. 48 this glass is shown with its nose 
pieces properly adapted to the sides of the nose. Any con- 
formation may be required, but that shown in Fig. 48 is 
the one most frequently needed. These changes in the 




Fig. 48. 



shape of the nose pieces are readily effected by means of 
the square-jawed pliers, especially if the so-called shell 
guards are used. The celluloid of which they are really 
made is, together with its gold backing, readily molded 
into whatever shape is desired. When the guards are of 
cork, care must be taken that they are not scarred and 
broken by the pliers, and a special tool with a longitudinal 
groove in the jaws for grasping the sides of the nose pieces 
is here of service. 

Having conformed the nose pieces to their bony support, 
the tension of the spring by which they are pressed against 
the sides of the nose is to be regulated, the object being to 



INSPECTION AND ADJUSTMENT OF SPECTACLES. 



99 



have just sufificient force exerted to keep the guards 
securely in place. If the latter are properly fitted the 
amount of pressure necessary is not great. Though this 
pressure should be evenly distributed over the surfaces of 
the nose pieces, want of firmness in the ''pinch" of their 
tops is particularly fatal, as the lower ends then become 
the principal support of the weight of the glasses, render- 
ing them prone to topple forward and fall. To increase 
the tension of the spring, and consequently the pinch of 




Fig. 49. 



the frames, the curve of the spring included between the 
lines at A, in Fig. 49, should be made more arched and 
rounded. Conversely, the force of the spring is lessened 
by flattening this arch. Any alteration in the shape of the 
spring, however, while it does not, of course, change the 
shape of the nose pieces, does change the angle at which 
they are inclined to each other. For instance, if the spring 
be made more arched, the nose pieces are brought nearer 
together, but the bottoms are especially approached toward 
each other. When the spring is flattened the bottoms of 



lOO SPECTACLES AND EYEGLASSES. 

the nose pieces are thrown proportionately farther apart 
than the tops. It follows that with each adjustment of the 
tension of the spring the inclination of the nose pieces 
must be rectified. This is easily accomplished by twisting 
the ''foot" or support of the nose piece at b in Fig. 49. 
It will be readily seen, moreover, that the nose pieces must 
incline equally to a vertical plane passing through the 
center of the nose ; otherwise the glasses will stand awry. 

When the points mentioned have been properly ad- 
justed, the long axis of one or both glasses may fail to 
stand squarely across the face as it should do. The remedy 
lies in an appropriate bend of the spring at the point c 
(Fig. 49). This also requires a slight re-adjustment of the 
inclination of the nose pieces to each other. 

The distance between the centers of eyeglasses is deter- 
mined (the distance between the nose pieces when in use 
being a fixed quantity) by the distance of the nose piece on 
each side from the center of the corresponding eye. The 
intercentral measurement may therefore be varied by vary- 
ing the size of the eye used, and by altering the distance 
of the nose pieces from the edges of the lenses by an 
appropriate bend of the foot b (Fig. 49). The distance of 
the glasses from the eye is controlled by the length of the 
foot B, and in the better grades of goods this part is made 
in two or three lengths. 

The Care of Spectacles. — Spectacle frames will last 
longer and perform their function better if the wearer is 
instructed to exercise care in handling them. In putting 
them on and off, the hooks should be lifted from or into 
their position behind the ears; both hands being used, so 
as to avoid straining the temples widely apart or otherwise 
bending them. They should be folded together as little as 
possible, and when not in use should be laid in a safe place, 



INSPECTION AND ADJUSTMENT OF SPECTACLES. 1 01 

open, and resting on the edges of the lenses, to avoid 
scratching the surfaces of the latter. For cleansing them 
nothing is better than a piece of clean old linen, or, if very 
much soiled, a little ammonia and water may be used, ex- 
cept on cemented bifocal glasses. While cleansing, the 
frame should be grasped by the end piece and not by the 
bridge, and in replacing the glasses on the eyes care 
should be taken not to crush them against the lashes and 
thus soil the refracting surfaces at once. When cylindrical 
or prismatic glasses are worn, patients may return after a 
time with the statement that the spectacles are unsatisfac- 
tory, when the trouble will frequently be found to be due 
to bending of the frame ; or a lens may have fallen out and 
been replaced upside down, or with the wrong edge in- 
ward. It is well to have such persons report periodically 
to have their glasses re-adjusted. 



INDEX 



Adjustment of eyeglasses, 97 

of spectacles, 91 
Airy, discoverer of astigmatism, 23 
Alhazen, 19 
Ancient glass, 17 
Angle, deviating, of a prism, 84, 89 

refracting, 84, ^j 
Apex of a prism, finding the, %2> 
Assyrians, knowledge of lenses 

among, 18 
Astigmatism, discovery of, 23 
Asymmetry of the face, 97 

Bar spring eyeglasses, 46 
Bifocal glasses, 42 

invention of, 23 
varieties of, 44 
Brewster, Sir David, 18, 23 
Bridge, width of base of, 'j'^ 

relation of top of to plane of 

glasses, 58, 72 
height of, 71 
Bridges, manufacture of, 2,^ 
varieties of, 40 

Care of spectacles, 100 
Cemented bifocals, 44 
Centering and decentering, 49 

normal lateral, 55 

normal vertical, 56 

of spectacles for constant use, 55 
near work, 55, 57 
Centrad, 53, 85, 86, 90 
Chemical composition of glass, 29 
Component parts of spectacles, 27 
Conformation of nose pieces, 98 
Crown glass, 29 
Cylinder, finding the axis of, 81 



Decentered lenses, 50 

prismatic effect of, 51 
Deviating angle of a prism, 84, 89 
Dioptric system, 33 
Di Spina, Alessandro, 20 
Discovery of astigmatism, 23 
Distance between the pupils, 51, 67 

between temples, 94 

of the glasses from the eyes, 57 

Emerald used by Nero, 18 
Epicanthus, eyeglasses for, 48 
Eyeglasses, advantages and disadvan- 
tages of, 26 
inspection and adjustment of, 76, 

97 

prescription of, 75 

varieties of, 46 
Extra front, 45 
Eye wires, manufacture of, 38 

Face, asymmetry of, 70, 74, 97 

Facing of spectacles, 58 

Focal length of lenses, 76 

Frames (see spectacle frames) 

Frameless spectacles, 39 

Franklin, inventor of bifocal glasses, 

glasses, 42 

Geometrical center, 49 

Glass, chemical composition of, 29 

ancient, 17 
Ground bifocals, 44 

Height of bridge, 71 
Hook temples, 38, 95 



Date of invention of spectacles, 20 i Index of refraction, 30 

103 



104 



INDEX. 



Inspection and adjustment of specta- 
cles, 76 
Interpupillary distance, 51, 65, 67 
Introduction, 17 
Invention of spectacles, 20 
Irregularity of surface of lenses, 91 

Kepler, Johann, 22 

Lateral centering, 55 
Lathe for grinding lenses, 34 
Lens cutter, 35 

oldest known, 18 
Lenses, decentered, 50 

finding focal length of, 76 

forms of, 30 

known to the ancients, 18 

material of, 28 

method of grinding, 34 

neutralization of spherical, 79 
cylindrical, 80 
sphero-cylindrical, 81 

numeration of, ^^ 

proving the strength of, 76 

toric, 37, 63 

tilted, 58 
Locating the optical center, 82 
Lorgnettes, 26 

Maddox pupil localizer, 69 

Marking of gold spectacle frames, 27 

Material of lenses, 28 

of spectacle frames, 26 
Meniscus, 31 

Natural position for spectacle bridge, 

Nero, concave jewel used by, 18 
Neutralization of spherical lenses, 79 
cylindrical lenses, 80 
sphero-cylindrical lenses, 81 
New system of numbering lenses, 1,3 
Normal position of spectacles, 49 
Nose pieces, conformation of, 98 
Numeration of lenses, ;^3 
of prisms, 84 

Offset guard, 46 

Oldest knowm lens, 18 

Old system of numbering lenses, ^^ 

Opticians' lathe, 34 



Optical center, 49 

locating the, 82 

Pebble spectacles, 29 

Periscopic glasses, 36, 62 

Pince nez (see eyeglasses) 

Phacometers, 77 

Plane of the glasses, relation to the 
I visual axis, 58 
I Prism diopter, 84 
i finding the apex of, S3 

I deviating angle of, 84, 89 

I refracting angle of, 84, Sj 

! numeration of, 84 

Prismatic effect of decentering, 51 
j Prismetry, Sj 

j Prescription blank for spectacles, 67 
I of eyeglasses, 75 

of frames, 65 
; Proving the strength of lenses, 76 
[ Principal axis, 49 

Principles of spectacle fitting, 49 
' Pupil localizer, 69 

Pupillometer, 70 

Quizzing glasses, 26 

Refracting angle of a prism, 84, 87 

surfaces, 30 
Rigid frame eyeglasses, 46 
Rock crystal, 18, 29 
Romans, knowledge of lenses among, 

18 
Rule for measuring frames, 65 

Saddle bridge, 40 

Salvinus Armatus, 20 

Scratches, specks, flaws, etc., in glass. 

Signs used in prescription writing, 32 

Spectacle eyes, sizes of, 42 
shapes of, 41 
fitting, principles of, 49 
frames, adjustment of, 91 
material of, 26 
marking of gold, 27 
prescription of, 65 
rule for measuring, 65 - 

Spectacles, component parts of, 27 
bifocal, 42 



INDEX. 



105 



Spectacles, care of, 100 

date of invention of, 20 

early references to, 20, 21 

for cosmetic effect, 48 

invention of bifocal, 23 

inspection and adjustment of, 76 

frameless, 39 

facing of, 58 

patterns of, ^S 

pebble, 29 

periscopic, 36, 62 

reversible, 40 
St. Jerome's eyeglasses, 21 
Surface, irregularity of, 91 



Temples, manufacture of, ^S 
■ varieties of, 40 

! Tilted lenses, 58 
! " Tool " for grinding spherical lenses, 

Tools for adjusting frames, 91 
I Toric lenses, 37, 63 
I Transparent glass found in Nineveh, 

17 

Trial frames, 69, 74 

j Vertical centering, 56 

i Visual axis, relation of plane of the 

j glasses to, 58 



Temples, distance between, 94 



Width of base of bridge, 73 



Catalogue No. S. October, 1895. 



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311 Illustrations. Cloth, ^2.50; Oil-Cloth, 1^2.50; Leather, $3.00 
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The General and Microscopical Structure of Bone and its Develop- 
ment. With Lithographic Plates and numerous Illus. 7th Ed. ^5.25 
HOLDEN. Landmarks. Medical and Surgical. 4th Ed. ^1.00 
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With Special Reference to the Requirements of Practical Surgery and 
Medicine. 816 Illustrations, 400 of which are original. 

Cloth, $5.00 ; Leather, ^6.00 
MARSHALL. Physiological Diagrams. Life Size, Colored. 
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In Sheets, Unmounted, ^40.00; Backed with Muslin and Mounted 
on Rollers, ^60.00; Ditto, Spring Rollers, in Handsome Walnut Wall 
Map Case (send for special circular), ^100.00; Single Plates — Sheets, 
S5.00; Mounted, ^7.50. Explanatory Key, .50. Descriptive circu- 
lar upon application. 
POTTER. Compend of Anatomy, Including Visceral Anatomy. 
5th Edition. 16 Lithographed Plates and 117 other Illustrations. 

.80; Interleaved, ^1.25 

WILSON. Human Anatomy, nth Edition. 429 Illustrations, 26 

Colored Plates, and a Glossary of Terms. $5.00 

OBERSTEINER. Anatomy of the Central Nervous Organs. 

198 Illustrations. ^5-5o 



ANESTHETICS. 

BUXTON. On Anesthetics. 2d Edition. Illustrated. ^1.25 

TURNBULL. Artificial Anesthesia. The Advantages and 
Accidents of; Its Employment in the Treatment of Disease ; Modes 
of Administration ; Considering their Relative Risks ; Tests of 
Purity ; Treatment of Asphyxia ; Spasms of the Glottis ; Syncope, 
etc. 3d Edition, Revised. 40 Illustrations. $3.00 



SUBJECT CATALOGUE. 



BRAIN AND INSANITY. 

BLACKBURN. A Manual of Autopsies. Designed for the Use 
of Hospitals for the Insane and other Public Institutions. Ten full- 
page Plates and other Illustrations. $1.25 

GOWERS. Diagnosis of Diseases of the Brain. 2d Edition. 
Illustrated. $1.50 

HORSLEY. The Brain and Spinal Cord. The Structure and 
Functions of. Numerous Illustrations. $2.50 

HYSLOP. Mental Physiology. Especially in Relation to Men- 
tal Disorders. With Illustrations. Just Ready. $4.25 

LEWIS (BEVAN). Mental Diseases. A Text-Book Having 
Special Reference to the Pathological Aspects of Insanity. 18 Litho- 
graphic Plates and other Illustrations. J^S-oo 

MANN. Manual of Psychological Medicine and Allied 
Nervous Diseases. Their Diagnosis, Pathology, Prognosis, and 
Treatment, including their Medico-Legal Aspects ; with chapter on 
Expert Testimony, and an Abstract of the Laws Relating to the 
Insane in all the States of the Union. Illustrations of Typical Faces 
of the Insane, Handwriting of the Insane, and Micro-photographic 
Sections of the Brain and Spinal Cord. $3.00 

REGIS. Mental Medicine. Authorized Translation by H. M. 
Bannister, m.d. ^2.00 

STEARNS. Mental Diseases. Designed especially for Medical 
Students and General Practitioners. With a Digest of Laws of the 
various States Relating to Care of Insane. Illustrated. 

Cloth, ^2.75; Sheep, $3.25 

TUKE. Dictionary of Psychological Medicine. Giving the 
Definition, Etymology, and Symptoms of the Terms used in Medical 
Psychology, with the Symptoms, Pathology, and Treatment of the 
Recognized Forms of Mental Disorders, together with the Law of 
Lunacy in Great Britain and Ireland. Two volumes. ^10.00 

WOOD, H. C. Brain and Overwork. .40 



CHEMISTRY AND TECHNOLOGY. 

special Catalogue of Che7nical Books sent free upon application. 

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Vol. I, Vol. II, Vol. Til, Part I. Ihese volumes cannot be had. 
Vol. Ill, Part II. The Amins. Pyridin and its Hydrozins and 
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Vol. III. Part III. In Press. 

ALLEN. Chemical Analysis of Albuminous and Diabetic 
Urine. $2.25 

BARTLEY. Medical and Pharmaceutical Chemistry. A 
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Illustrations, Glossary, and Complete Index. 3d Edition, carefully 
Revised. Cloth, ^2.75 ; Sheep, ^3.25 

BLOXAM. Chemistry, Inorganic and Organic. With Experi- 
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MEDICAL BOOKS. 5 

CALDWELL. Elements of Qualitative and Quantitative 
Chemical Analysis. 3d Edition, Revised. $1.50 

CAMERON. Oils and Varnishes. With Illustrations, Formulae, 
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CAMERON. Soap and Candles. 54 Illustrations. $2.00 

CLOWES AND COLEMAN. Elementary Qualitative An- 
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GARDNER. The Brewer, Distiller, and Wine Manufac- 
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GARDNER. Bleaching, Dyeing, and Calico Printing. With 
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GROVES AND THORP. Chemical Technology. The Appli- 
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Vol. I. Fuel and Its Applications. 607 Illustrations and 4 Plates. 
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LEFFMANN. Compend of Medical Chemistry, Inorganic 
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.80 ; Interleaved, $1.25 

LEFFMANN. Progressive Exercises in Practical Chemis- 
try. Illustrated. 2d Edition, $1.00 

LEFFMANN. Analysis of Milk and Milk Products. Arranged 
to Suit the Needs of Analy tica.1 Chemists , Dairymen, and Milk Inspec- 
tors. ;^i.25 

LEFFMANN. Water Analysis, Illustrated. 3d Edition. ^1.25 

MUTER. Practical and Analytical Chemistry. 4th Edition. 
Revised to meet the requirements of American Medical Colleges by 
Claude C. Hamilton, m.d. 51 Illustrations. 1^1.25 

OVERMAN. Practical Mineralogy, Assaying, and Mining. 

With a Description of the Useful Minerals, etc. nth Edition. ^i.oo 

RAMSAY. A System of Inorganic Chemistry, lUus. $4.00 

RICKTER. Inorganic Chemistry. 4th American, from 6th Ger- 
man Edition. Authorized translation by Edgar F. Smith, m.a., 
PH.D. 89 Illustrations and a Colored Plate. $1-75 

RICHTER. Organic Chemistry. 2d American Edition. Trans, 
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SMITH. Electro-Chemical Analysis. 2d Edition, Revised. 28 
Illustrations. $1-25 

SMITH AND KELLER. Experiments. Arranged for Students 
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STAMMER. Chemical Problems. With Explanations and An- 
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the Quantitative Estimation of Chemical Substances by Measure, 
Applied to Liquids, Solids, and Gases. 6th Edition, Revised. With 
Illustrations. $4.50 



6 SUBJECT CATALOGUE. 

SYMONDS. Manual of Chemistry, for Medical Students. 

2d Edition. ' $2.00 

TRIMBLE. Practical and Analytical Chemistry. Being a 
Complete Course in Chemical Analysis. 4th Ed. lUus. $1.50 

WATTS. Organic Chemistry. 2d Edition. By Wm. A. Tilden, 
D.sc.,F.R.s. (Being the 13th Edition of Fowne's Organic Chemistry.) 
Illustrated. ^2.00 

^VATTS. Inorganic Chemistry. Physical and Inorganic. (Being 
the 14th Edition of Fowne's Physical and Inorganic Chemistry.) 
With Colored Plate of Spectra and other Illustrations. $2.00 

WOODY. Essentials of Chemistry and Urinalysis. 4th 
Edition. Illustrated. In Press. 



CHILDREN. 

GOODHART AND STARR. Diseases of Children. From the 
3d English Edition. Rearranged and Edited, with Notes and Addi- 
tions, by Louis Starr, m.d. Out 0/ Print. 

HALE. On the Management of Children in Health and Dis- 
ease. .50 

HATFIELD. Diseases of Children. With a Colored Plate. 2d 
Edition. Jiist Ready. ^ .80 ; Interleaved, $1.25 

MEIGS. Infant Feeding and Milk Analysis. The Examination 
of Human and Cow's Milk, Cream, Condensed Milk, etc., and 
Directions as to the Diet of Young Infants. .50 

MONEY. Treatment of Diseases in Children. Including the 
Outlines of Diagnosis and the Chief Pathological Differences Between 
Children and Adults. 2d Edition. ^2.50 

MUSKETT. Prescribing and Treatment in the Diseases of 
Infants and Children. $1.25 

POWER. Surgical Diseases of Children and their Treat- 
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STARR. The Digestive Organs in Childhood. The Diseases of 
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the Investigation of Disease and the Management of Children. 2d 
Edition, Enlarged. Illustrated by two Colored Plates and numerous 
Wood Engravings. ^2.00 

STARR. Hygiene of the Nursery. Including the General Regi- 
men and Feedmg of Infants and Children, and the Domestic Manage- 
ment of the Ordinary Emergencies of Early Life, Massage, etc. 4th 
Edition. 25 Illustrations. ^i.oo 



CLINICAL CHARTS. 

GRIFFITH. Graphic Clinical Chart. Printed in three colors. 
Sample copies free. Put up m loose packages of fifty, .50. Price to 
Hospitals, 500 copies, ^4.00 ; 1000 copies, ^7.50, With name of 
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TEMPERATURE CHARTS. For Recording Temperature, 
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MEDICAL BOOKS. 



DEFORMITIES. 

REEVES. Bodily Deformities and Their Treatment. A 

Hand-Book of Practical Orthopedics. 228 Illustrations. $i.75 

HEATH. Injuries and Diseases of the Jaws. 187 Illustrations. 

Cloth, ^4.50 

DENTISTRY. 

special Catalogtie of Dental Books sent free upon application. 

BARRETT. Dental Surgery for General Practitioners and 
Students of Medicine and Dentistry. Extraction of Teeth, 
etc. 2d Edition. Illustrated. ^1.00 

BLODGETT. Dental Pathology. By Albert N. Blodgett, 
M.D., late Professor of Pathology and Therapeutics, Boston Dental 
College. 33 Illustrations. $1.25 

FLAGG. Plastics and Plastic Filling, as Pertaining to the Filling 

' of All Cavities of Decay in Teeth below Medium in Structure, and to 

Difficult and Inaccessible Cavities in Teeth of all Grades of Structure. 

4th Edition. ;^4.oo 

FILLEBROWN. A Text-Book of Operative Dentistry. 
Written by invitation of the National Association of Dental Facul- 
ties. Illustrated. 1^2.25 

GORGAS. Dental Medicine. A Manual of Materia Medica and 
Therapeutics. 5th Edition, Revised. ^4,00 

HARRIS. Principles and Practice of Dentistry. Including 
Anatomy, Physiology, Pathology, Therapeutics, Dental Surgery, 
and Mechanism. 12th Edition. Revised by F. J. S. Gorgas, m.d., 
D.D.s. 1086 Illustrations. Cloth, ^6.00; Leather, ^7.00 

HARRIS. Dictionary of Dentistry. Including Definitions of Such 
Words and Phrases of the Collateral Sciences as Pertain to the Art and 
Practice of Dentistry. 5th Edition. Revised and Enlarged by Fer- 
dinand F. S. Gorgas, m d., d.d.s. Cloth, $4.50; Leather, ^5.50 

HEATH. Injuries and Diseases of the Jaws. 4th Edition. 187 
Illustrations. ^4.50 

HEATH. Lectures on Certain Diseases of the Jaws. 64 
Illustrations. Boards, .50 

RICHARDSON. Mechanical Dentistry. 6th Edition. Thor- 
oughly Revised by Dr. Geo. W. Warren. 600 Illustrations. 

Cloth, ^4.00 ; Leather, $5.00 

SEWELL. Dental Surgery. Including Special Anatomy and 
Surgery. 3d Edition, with 200 Illustrations. ^2 00 

TAFT. Operative Dentistry. A Practical Treatise. 4th Edition. 
100 Illustrations. Cloth, ^3.00 ; Leather, $4.00 

TAFT. Index of Dental Periodical Literature. ^2.00 

TALBOT. Irregularities of the Teeth, and Their Treatment. 
2d Edition. 234 Illustrations. $3. 00 

TOMES. Dental Anatomy. Human and Comparative. 235 Illus- 
trations. 4th Edition. ^3.50 
TOMES. Dental Surgery. 3d Edition. 292 Illustrations. ^4.00 
WARREN. Compend Dental Pathology and Dental Medi- 
cine. With a Chapter on Emergencies. Illustrated. 

.80; Interleaved, ;^i.25 
WARREN. Dental Prosthesis and Metallurgy. 129 Ills. ^1.25 
WHITE. The Mouth and Teeth. Illustrated. .4c 



8 SUBJECT CATALOGUE. 

DICTIONARIES. 

GOULD. The Illustrated Dictionary of Medicine, Biology, 
and Allied Sciences. Being an Exhaustive Lexicon of Medicine 
and those Sciences Collateral to it : Biology (Zoology and Botany), 
Chemistr}'-, Dentistry, Parmacology, Microscopy, etc., with many 
useful Tables and numerous fine Illustrations. 1633 pages. 

Sheep or Half Dark Green Leather, ^10.00; Thumb Index, $11.00 
Half Russia, Thumb Index, $12.00 

GOULD. The Medical Student's Dictionary. Including all the 
Words and Phrases Generally Used in Medicine, with their Proper 
Pronunciation and Definition, Based on Recent Medical Literature. 
With Tables of the Bacilli, Micrococci, Leucomains, Ptomains, etc., 
of the Arteries, Muscles, Nerves, Ganglia, and Plexuses, etc. 

Half Dark Leather, $2.75 ; Half Morocco, Thumb Index, $3.50 

GOULD. The Pocket Pronouncing Medical Lexicon. (12,000 
Medical Words Pronounced and Defined.) Containing all the Words, 
their Definition and Pronunciation, that the Medical, Dental, or 
Pharmaceutical Student Generally Comes in Contact With; also 
Elaborate Tables of the Arteries, Muscles, Nerves, Bacilli, etc., etc., 
a Dose List in both English and Metric System, etc., Arranged in a 
Most Convenient Form for Reference and Memorizing. 

Full Limp Leather, Gilt Edges, $i.oo; Thumb Index, $1.25 
*^* Sample Pages and Illustrations and Descriptive Circulars of 

Gould's Dictionaries sent free upon application. 

HARRIS. Dictionary of Dentistry. Including Definitions of Such 
Words and Phrases of the Collateral Sciences as Pertain to the Art 
and Practice of Dentistry. 5th Edition. Revised and Enlarged by 
Ferdinand J. S. GoRciAS, m.d., d.d.s Cloth, $4.50; Leather, $5.50 

LONGLEY. Pocket Medical Dictionary. Giving the Definitionand 
Pronunciation of Words and Terms in General Use in Medicine and 
Collateral Sciences, with an Appendix, containing Poisons and their 
Antidotes, Abbreviations used in Prescriptions, and a Metric Scale 
of Doses. Cloth, .75; Tucks and Pocket, $1.00 

CLEVELAND. Pocket Medical Dictionary. 33d Edition. Very 
small pocket size. Cloth, .50 ; Tucks with Pocket, .75 

MAXWELL, Terminologia Medica Polyglotta. By Dr. 
Theodore Maxwell, Assisted by Others. $3-oo 

The object of this work is to assist the medical men of any nationahty 

in reading medical literature written in a language not their own. 

Each term is usually given in seven languages, viz, : English, French, 

German, Italian, Spanish, Russian, and Latin. 

TREVES AND LANG. German-English Medical Dictionary. 

Half Russia, ^3.25 

EAR (see also Throat and Nose). 

HOVELL. Diseases of the Ear and Naso-Pharynx. Includ- 
ing Anatomy and Physiology of the Organ, together with the Treat- 
ment of the Affections of the Nose and Pharynx which Conduce to 
Aural Disease. 122 Illustrations. $5.00 

BURNETT. Hearing and How to Keep It. Illustrated. .40 

DALBY. Diseases and Injuries of the Ear. 4th Edition. 28 
Wood Engravings and 7 Colored Plates. ^2.50 

HALL. Compend of Diseases of Ear and Nose. Illustrated. 

.80 ; Interleaved, $1.25 

PRITCHARD. Diseases of the Ear. 2d Edition. Many Illus- 
trations and Formulae. $1.25 



MEDICAL BOOKS. 



ELECTRICITY. 

BIGELOW. Plain Talks on Medical Electricity and Bat- 
teries. With a Therapeutic Index and a Glossary. . 43 Illustra- 
tions. 2d Edition. $1.00 

MASON. Electricity, Its Medical and Surgical Uses. Numer- 
ous Illustrations. .75 

STEAVENSON AND JONES. Medical Electricity. 2d Edi- 
tion. 103 Illustrations. Preparing. 

EYE. 

A Special Circular of Books on the Eye sent free upon application. 

ARLT. Diseases of the Eye. Clinical Studies on Diseases of the 
Eye, Including the Conjunctiva, Cornea and Sclerotic, Iris and 
Ciliary Body. Authorized Translation by Lyman Ware, m. d. 
Illustrated. $1.25 

FICK. Diseases of the Eye and Ophthalmoscopy. Trans- 
lated by A. B. Hale, m. d. 157 Illustrations, many of which are in 
colors. In Press. 

FOX AND GOULD. Compend on Diseases of the Eye and 
Refraction, Including Treatment and Surgery. 2d Edition. 71 
Illustrations and 39 Formulae. .80; Interleaved, ^1.25 

GOWERS. Medical Ophthalmoscopy. A Manual and Atlas 
with Colored Autotype and Lithographic Plates and Wood-cuts, 
Comprising Original Illustrations of the Changes of the Eye in Dis- 
eases of the Brain, Kidney, etc. 3d Edition. ^4.00 

HARLAN. Eyesight, and How to Care for It. Illus. .40 

HARTRIDGE. Refraction. 96 Illustrations and Test Types. 
7th Edition. ^too 

HARTRIDGE. On the Ophthalmoscope. 2d Edition. With 
Colored Plate and many Wood-cuts. ^1.25 

HANSELL AND BELL. Clinical Ophthalmology. Colored 
Plate of Normal Fundus and 120 Illustrations. $1.50 

HIGGENS. Ophthalmic Practice. Illustrated. $1.50 

MACNAMARA. On the Eye. 5th Edition, Numerous Colored 
Plates, Diagrams of Eye, Wood-cuts, and Test Types. $3-5^ 

MEYER. Ophthalmology. A Manual of Diseases of the Eye. 
Translated from the 3d French Edition by A. Freedland Fergus, 
M. B. 270 Illustrations, 2 Colored Plates. Cloth, $3.50; Sheep, $4.50 

MORTON. Refraction of the Eye. Its Diagnosis and the Cor- 
rection of its Errors. With Chapter on Keratoscopy and Test 
Types. 5th Edition. ^i.oo 

PHILLIPS. Spectacles and Eyeglasses. Their Prescription 
and Adjustment. 2d Edition. 47 Illustrations. In Press. 

S\A^ANZY. Diseases of the Eye and Their Treatment. 4th 
Edition. 164 Illustrations. 2 Colored and i Plain Plate, and a 
Zephyr Test Card. Cloth, $2.50; Sheep, $3.00 

WALKER. Students' Aid in Ophthalmology. Illustrations 
and Glossary. In Press. 

FEVERS. 

COLLIE. On Fevers. Their History, Etiology, Diagnosis, Prog- 
nosis, and Treatment. Colored Plates. J2.C0 



10 SUBJECT CATALOGUE, 



GOUT AND RHEUMATISM. 

DUCKWORTH. A Treatise on Gout. With Chromo-lithographs 
and Engravings Cloth, ^6.00 

GARROD. On Rheumatism. A Treatise on Rheumatism and 
Rheumatic Arthritis. Cloth, $5.00 

HAIG. Causation of Disease by Uric Acid. A Contribution to 
the Pathology of High Arterial Tension, Headache, Epilepsy, Gout, 
Rheumatism, Diabetes, Bright's Disease, etc. New Ed, In Press. 



HEADACHES, 

DAY. On Headaches. The Nature, Causes, and Treatment of 

Headaches. 4th Edition. Illustrated. ^1,00 



HEALTH AND DOMESTIC MEDI- 
CINE (see also Hygiene and Nursing). 

BUCKLEY. The Skin in Health and Disease. Illus. .40 

BURNETT. Hearing and How to Keep It. Illustrated .40 

COHEN. The Throat and Voice. Illustrated. .40 

DULLES. "What to Do First in Accidents and Poisoning. 

4th Edition. New Illustrations, Jgi.oo 

HARLAN. Eyesight and How to Care for It. Illustrated. .40 
HARTSHORNE. Our Homes, their Situation, Construction, 

Drainage, etc. Illustrated. .40 

OSGOOD. The Winter and its Dangers. .40 

PACKARD. Sea Air and Bathing. .40 

PARKES. The Elements of Health. Just Ready. $1.25 

RICHARDSON. Long Life and How to Reach It. .40 

WESTLAND. The Wife and Mother. A Hand-Book for 

Mothers. $1.50 

WHITE. The Mouth and Teeth. Illustrated. .40 

W^ILSON. The Summer and its Diseases. .40 

WOOD. Brain W^ork and Overwork. .40 

STARR. Hygiene of the Nursery. 4th Edition. ^i.oo 

CANFIELD. Hygiene of the Sick-Room. ^1.25 



HEART. 

SANSOM. Diseases of the Heart. The Diagnosis and Pathology 
of Diseases of the Heart and Tnoracic Aorta. With Plates and other 
Illustrations. $6.00 



MEDICAL BOOKS. 11 

HYGIENE AND WATER ANALYSIS. 

Special Catalogue q/ Books on Hygiene sent free upon application. 

CANFIELD. Hygiene of the Sick-Room. A Book for Nurses 
and Others. Being a Brief Consideration of Asepsis, Antisepsis, Dis- 
infection, Bacteriology, Immunity, Heating and Ventilation, and 
Kindred Subjects. $1.25 

COPLIN AND BEVAN. Practical Hygiene. A Complete 
American Text-Book. 138 Illustrations. ^3-25 

FOX. Water, Air, and Food. Sanitary Examinations ofWater, 
Air, and Food. 100 Engravings. 2d Edition, Revised. $3'5o 

KENWOOD. Public Health Laboratory Work. 116 Illustra- 
tions and 3 Plates. ;^2.oo 

LEFFMANN. Examination of W^ater for Sanitary and 
Technical Purposes. 3d Edition. Illustrated. Just Ready, $1.25 

LEFFMANN. Analysis of Milk and Milk Products. Illus- 
trated. ^1.25 

LINCOLN. School and Industrial Hygiene. .40 

MACDONALD. Microscopical Examinations of W^ater and 
Air. 25 Lithographic Plates, Reference Tables, etc. 2d Ed. $2.50 

McNEILL. The Prevention of Epidemics and the Construc- 
tion and Management of Isolation Hospitals. Numerous Plans 
and Illustrations. ^3.50 

PARKES. Practical Hygiene. 8th Edition. Edited by J. Lane 
Notter. ID Lithographic Plates and over 100 other Illustrations. ^4.50 

PARKES. Hygiene and Public Health. By Louis C. Parkes, 
M.D. 4th Edition. Enlarged. Illustrated. ^2.50 

PARKES. Popular Hygiene. The Elements of Health. A Book 
for Lay Readers. Illustrated. Just Ready. $1.25 

STARR. The Hygiene of the Nursery. Including the General 
Regimen and Feeding of Infants and Children, and the Domestic 
Management of the Ordinary Emergencies of Early Life, Massage, 
etc. 4th Edition. 25 Illustrations, ^i.oo 

STEVENSON AND MURPHY. A Treatise on Hygiene. By 
Various Authors. In Three Octave Volumes. Illustrated. 

Vol. I, $6.00; Vol. II, $6.00; Vol. Ill, $5.00 
*:{:* Each Volume sold separately. Special Circular upon application. 

W^ILSON. Hand-Book of Hygiene and Sanitary Science. 

Wiih Illustrations. 7th Edition $3.00 

WEYL. Sanitary Relations of the Coal-Tar Colors. Author- 
ized Translation by Henry Leffmann, m.d., ph.d. ^1.25 



JOURNALS, ETC. 



OPHTHALMIC REVIEW. A Monthly Record of Ophthalmic 
Science. Publ. in London. Sample number .25 ; per annum ^3.00 

NEW SYDENHAM SOCIETY PUBLICATION. Three to six 
volumes each year. Circular upon application. Per annum ^8.00 



12 SUBJECT CATALOGUE. 

KIDNEY DISEASES. 

RALFE. Diseases of the Kidney and Urinary Derange- 
ments. Illustrated. ^2.00 
THORNTON. The Surgery of the Kidney. 19 Illus. Clo., $1.50 
TYSON. Bright's Disease and Diabetes, With Especial "Re- 
ference to Pathology and Therapeutics. Including a Section on Reti- 
nitis in Bright's Disease. Illustrated. ^2.50 

LUNGS AND PLEURiE. 

HARRIS AND BEALE. Treatment of Pulmonary Consump- 
tion. In Press. 

POWELL. Diseases of the Lungs and Pleurae, including 
Consumption. Colored Plates and other Illus. 4th Ed. $4.00 

MASSAGE. 

KLEEN AND HART WELL. Hand-Book of Massage. Autho- 
rized translation by Mussey Hartwell, m.d., ph.d. With an In- 
troduction by Dr. S. Weir Mitchell. Illustrated by a series of 
Photographs Made Especially by Dr. Kleen for the American 
Edition. ^2.25 

MURRELL. Massotherapeutics. Massage as a Mode of Treat- 
ment. 5th Edition. i?l-25 

OSTROM. Massage and the Original Swedish Move- 
ments. Their Application to Various Diseases of the Body. A 
Manual for Students, Nurses, and Physicians. Third Edition, En- 
larged. 94 Wood Engravings, many of which are original. jSi.oo 

MATERIA MEDICA AND THERA- 
PEUTICS. 

ALLEN, HARLAN, HARTE, VAN HARLINGEN. A 
Hand-Book of Local Therapeutics, Beinga Practical Description 
of all those Agents Used in the Local Treatment of Diseases of the 
Eye, Ear, Nose and Throat, Mouth, Skin, Vagina, Rectum, etc., 
such as Ointments, Plasters, Powders, Lotions, Inhalations, Supposi- 
tories, Bougies, Tampons, and the Proper Methods of Preparing and 
Applying Them. fe.oo 

BIDDLE. Materia Medica and Therapeutics. Including Dose 
List, Dietary for the Sick, Table of Parasites, and Memoranda of 
New Remedies. 13th Edition, Thoroughly Revised in accord- 
ance with the new U. S. P. 64 Illustrations and a Clinical Index. 

Cloth, ^4.00; Sheep, $5.00 

BRACKEN. Outhnes of Materia Medica and Pharmacology. By 
H. M. Bracken, Professor of Materia Medica and Therapeutics 
and of Clinical Medicine, University of Minnesota. $2.75 

DAVIS. Materia Medica and Prescription Writing. $1.50 

FIELD. Evacuant Medication. Cathartics and Emetics. $1.75 

GORGAS. Dental Medicine. A Manual of Materia Medica and 
Therapeutics. 5th Edition, Revised. $4.00 

MAYS. Therapeutic Forces ; or, The Action of Medicine in 
the Light of Doctrine of Conservation of Force. 1^1.25 

MAYS. Theine in the Treatment of Neuralgia. Y^ bound, .50 



MEDICAL BOOKS. 



NAPHEYS. Modern Therapeutics, gth Revised Edition, En- 
larged and Improved. In two handsome volumes. Edited by Allen 
J. Smith, m.d., and J. Aubrey Davis, m.d. 

Vol. I. General Medicine and Diseases of Children. $4.co 

Vol. II. General Surgery, Obstetrics, and Diseases of Women. ^400 

POTTER. Hand-Book of Materia Medica, Pharmacy, and 
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mulae. 5th Edition, Revised and Enlarged. With Thumb Index in 
each copy. Cloth, $4.00; Sheep, $5.00 

POTTER. Compend of Materia Medica, Therapeutics, and 
Prescription \Vriting, with Special Reference to the Physiologi- 
cal Action of Drugs. 6th Revised and Improved Edition, based upon 
the U. S. P. 1890. .80; Interleaved, ^1.25 

SAYRE. Organic Materia Medica and Parmacognosy. An 
Introduction to the Study of the Vegetable Kingdom and the Vege- 
table and Animal Drugs. Comprising the Botanical and Physical 
Characteristics, Source, Constituents, and Pharmacopeial Prepara- 
tions. With chapters on Synthetic Organic Remedies, Insects Iii 
jurious to Drugs, and Pharmacal Botany. A Glossary and 543 Illus- 
trations, many of which are original. ^4.00 

WARING. Practical Therapeutics. 4th Edition, Revised and 
Rearranged. Cloth, ^2.00; Leather, $3.00 

WHITE AND WILCOX. Materia Medica, Pharmacy, Phar- 
macology, and Therapeutics. 2d American Edition, Revised by 
Reynold W. Wilcox, m.a., m.d., ll.d. Clo., $2.75; Lea., ^3.25 



MEDICAL JURISPRUDENCE AND 
TOXICOLOGY. 

REESE. Medical Jurisprudence and Toxicology. A Text-Book 
for Medical and Legal Practitioners and Students. 4th Edition. 
Revised by Henry Leffmann, m.d. Clo., ^3.00 ; Leather, $3.50 
" To the student of medical jurisprudence and toxicology it is in- 
valuable, as it is concise, clear, and thorough in every respect." — The 
Ainerican Journal of the Medical Sciences. 

MANN. Forensic Medicine and Toxicology. Illus. ^6.50 

MURRELL. What to Do in Cases of Poisoning. 7th 

Edition, Enlarged. ^i.oo 

TANNER. Memoranda of Poisons. Their Antidotes and Tests. 
7th Edition. .75 

MICROSCOPY. 

BEALE. The Use of the Microscope in Practical Medicine. 

For Students and Practitioners,with Full Directions for Examining the 
Various Secretions, etc., by the Microscope. 4th Ed. 500IIIUS. $6.50 

BEALE. How to W^ork with the Microscope. A Complete 
Manual of Microscopical Manipulation, containing a Full Description 
of many New Processes of Investigation, with Directions for Examin- 
ing Objects Under the Highest Powers, and for Taking Photographs 
of Microscopic Objects. 5th Edition. 400 Illustrations, many of 
them colored. $6.50 

CARPENTER. The Microscope and Its Revelations. 7th 
Edition. 800 Illustrations and many Lithographs. $5-5o 



14 SUBJECT CATALOGUE. 



LEE. The Microtomist's Vade Mecum. A Hand-Book of 
Methods of Microscopical Anatomy. 88i Articles. 4th Edition, 
Enlarged. In Press. 

MACDONALD. Microscopical Examinations of Water and Air. 

25 Lithographic Plates, Reference Tables, etc. 2d Edition. $2.50 
REEVES. Medical Microscopy, including Chapters on Bacteri- 
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trations, some of which are printed in colors. $2.50 
WETHERED. Medical Microscopy. A Guide to the Use of the 
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BLACK. Micro-Organisms. The Formation of Poisons. A 
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BURNETT. Foods and Dietaries. A Manual of Clinical Diet- 
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DAVIS. Biology. Illustrated. ^3.00 
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Rheumatism, Diabetes, Bright's Disease, etc. New Ed. In Press. 
HARE. Mediastinal Disease. Illustrated by six Plates. ^2.00 
HENRY. A Practical Treatise on Anemia. Half Cloth, .50 
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LEFFMANN. The Coal-Tar Colors. With Special Reference to 
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TREVES. Physical Education : Its Effects, Value, Methods. 
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LIZARS. The Use and Abuse of Tobacco. .40 
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GOWERS. Manual of Diseases of the Nervous System. A 

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parts Rewritten. With many new Illustrations. Two volumes. 
Vol. I. Diseases of the Nerves and Spinal Cord. $3.00 

Vol. II. Diseases of the Brain and Cranial Nerves; General and 
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GOWERS. Syphilis and the Nervous System. $1.00 

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GOWERS. Clinical Lectures. A New Volume of Essays on the 
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FLOWER. Diagram of the Nerves of the Human Body. 
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MEDICAL BOOKS. 15 



HORSLEY. The Brain and Spinal Cord. The Structure and 
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OBERSTEINER. The Anatomy of the Central Nervous Or- 
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ORMEROD. Diseases of the Nervous System. 75 Wood En- 
gravings. $1.00 

OSLER. Cerebral Palsies of Children. A Clinical Study. $2.00 

OSLER. Chorea and Choreiform Affections. ;^2.oo 

PAGE. Injuries of the Spine and Spinal Cord. In their Surgical 
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PAGE. Railroad Injuries. With Special Reference to Those of the 
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THORBURN. Surgery of the Spinal Cord. Illustrated. $4.00 

"WATSON. Concussions. An Experimental Study of Lesions Aris- 
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WOOD. Brain Work and Overwork. .40 



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CANFIELD. Hygiene of the Sick-Room. A Book for Nurses and 
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CULLINGWQRTH. A Manual of Nursing, Medical and Sur- 
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CULLINGWORTH. A Manual for Monthly Nurses. 3d Ed. .40 

DOMVILLE. Manual for Nurses and Others Engaged in At- 
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FULLERTON. Obstetrical Nursing. 38 Ills. 4th Ed. $1.25 

FULLERTON. Nursing in Abdominal Surgery and Diseases 
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HUMPHREY. A Manual for Nurses. Including General 
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SHAWE. Notes for Visiting Nurses, and all those Interested 
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Organization and Working of Various Visiting and District Nurse So- 
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STARR. The Hygiene of the Nursery. Including the General 
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TEMPERATURE CHARTS. For Recording Temperature, Res- 
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VOSWINKEL. Surgical Nursing, iii Illustrations. $1.00 



16 SUBJECT CATALOGUE. 

OBSTETRICS. 

BAR. Antiseptic Midwifery. The Principles of Antiseptic Meth- 
ods Applied to Obstetric Practice. Authorized Translation by 
Henry D. Fry, m.d., with an Appendix by the Author. |i.oo 

CAZEAUX AND TARNIER. Midwifery. With Appendix by 
MuNDH. The Theory and Practice of Obstetrics, including the Dis- 
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other full-page Plates, seven of which are beautifully colored, and 
numerous Wood Engravings. Cloth, $4.50 ; Full Leather, $5.50 

DAVIS. A Manual of Obstetrics. Being a Complete Manual for 
Physicians and Students. 2d Edition. 16 Colored and other Plates 
and 134 other Illustrations. $2.00 

LANDIS. Compend of Obstetrics. 5th Edition, Revised by Wm. 
H. Wells, Assistant Demonstrator of Clinical Obstetrics, Jeflferson 
Medical College. With many Illustrations, .80 ; Interleaved, ^1.25. 

SCHULTZE. Obstetrical Diagrams. Being a series of 20 Col- 
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wifery, with accompanying explanatory (German) text illustrated 
by Wood Cuts. 2d Revised Edition. 

Price in Sheets, ^26.00 ; Mounted on Rollers, Muslin Backs, ^36.00 

STRAHAN. Extra-Uterine Pregnancy. The Diagnosis and 
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WINCKEL. Text-Book of Obstetrics, Including the Pathol- 
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Translation by J. Clifton Edgar, a.m., m d. With nearly 200 Illus- 
trations. Cloth, ^5.00 ; Leather, ^6.00 

FULLERTON. Obstetrical Nursing. 4th Ed. Illustrated. ^1.25 



PATHOLOGY AND HISTOLOGY. 

BLACKBURN. Autopsies. A Manual of Autopsies Designed for 
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Ten full-page Plates and other Illustrations. $1.25 

BLODGETT. Dental Pathology. By Albert N. Blodgett, 
M.D., late Professor of Pathology and Therapeutics, Boston Dental 
College. 33 Illustrations. $1-25 

GILLIAM. Pathology. A Hand-Book for Students. 47 Illus. .75 

HALL. Compend of General Pathology and Morbid Anatomy. 
91 very fine Illustrations. .80; Interleaved, $1.25 

STIRLING. Outlines of Practical Histology. 368 Illustrations. 
2d Edition, Revised and Enlarged. With new Illustrations. $2.00 

VIRCHOW. Post-Mortem Examinations. A Description and 
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of the Berlin Charity Hospital, with Special Reference to Medico- 
legal Practice. 3d Edition, with Additions. .75 



PHARMACY. 

special Catalogue of Books on Phartnacy sent free upon application. 

COBLENTZ. Manual of Pharmacy. A New and Complete 
Text-Book by the Professor in the New York College of Pharmacy. 
395 Illustrations. $3-5«> 



MEDICAL BOOKS. 17 

BEASLEY. Book of 3100 Prescriptions. Collected from the 
Practice of the Most Eminent Physicians and Surgeons — English, 
French, and American. A Compendious History of the Materia 
Medica, Lists of the Doses of all the Officinal and Established Pre- 
parations, an Index of Diseases and their Remedies. 7ih Ed. ;$2,oo 

BEASLEY. Druggists' General Receipt Book. Comprising 
a Copious Veterinary Formulary, Recipes in Patent and Proprietary 
Medicines, Druggists' Nostrums, etc. ; Perfumery and Cosmetics, 
Beverages, Dietetic Articles and Condiments, Trade Chemicals, 
Scientific Processes, and an Appendix of Useful Tables. loth Edi- 
tion, Revised. $2.00 

BEASLEY. Pocket Formulary. A Synopsis of the British and 
Foreign Pharmacopoeias. Comprising Standard and Approved 
Formulae for the Preparations and Compounds Employed in Medical 
Practice, nth Edition. ^2.00 

PROCTOR. Practical Pharmacy. Lectures on Practical Phar- 
macy. With Wood Engravings and 32 Lithographic Fac-simile 
Prescriptions. 3d Edition, Revised, and with Elaborate Tables of 
Chemical Solubilities, etc. $3-oo 

ROBINSON. Latin Grammar of Pharmacy and Medicine. 
2d Edition. $i-75 

SAYRE. Organic Materia Medica and Pharmacognosy. An 
Introduction to the Study of the Vegetable Kingdom and the Vege- 
table and Animal Drugs. Comprising the Botanical and Physical 
Characteristics, Source, Constituents, and Pharmacopeial Prepar- 
ations. With Chapters on Synthetic Organic Remedies, Insects 
Injurious to Drugs, and Pharmacal Botany. A Glossary and 543 
Illustrations, many of which are original. $4.00 

SCOVILLE. The Art of Compounding. A Text-Book for the 
Student and a Reference Book for the Pharmacist. Nearly Ready. 

STEWART. Compend of Pharmacy. Based upon ** Reming- 
ton's 'lext-Book of Pharmacy " 5th Edition, Revised in Accord- 
ance with the U. S. Pharmacopoeia, 1890. Complete Tables of 
Metric and English Weights and Measures. .80; Interleaved, $1.25 

UNITED STATES PHARMACOPCEIA. 1890. 7th Decennial 
Revision. Cloth, $2.50 (postpaid, $2.77); Sheep, $3.00 (postpaid, 
^3.27); Interleaved, $4.00 (postpaid, ^4.50); Printed on one side ot 
page only, unbound, $3.50 (postpaid, $3.90). 

Select Tables from the U. S. P. (1890). Being Nine of the Most 
Important and Useful Tables, Printed on Separate Sheets. Care- 
fully put up in patent envelope. .25 

WHITE AND WILCOX. Materia Medica, Pharmacy, Phar- 
macology, and Therapeutics. 2d American Edition. Revised 
by Reynold W. Wilcox, m.d.,ll.d. Cloth, ^2 75; Leather, $3.25 

POTTER. Hand-Book of Materia Medica, Pharmacy, and 
Therapeutics. 600 Prescriptions and Formulae. 5th Edition. 

Cloth, $4.00; Sheep, ^5.00 



PHYSICAL DIAGNOSIS. 

TYSON. Hand-Book of Physical Diagnosis. For Students and 
Physicians. By the Professor of Clinical Medicine in the University 
of Pennsjdvania. Illus. 2d Ed., Improved and Enlarged. ^1.25 

MEMMINGER. Diagnosis by the Urine. 23 Illus. $1.00 

2 



18 SUBJECT CATALOGUE. 



PHYSIOLOGY. 

BRUBAKER. Compend of Physiology. 7th Edition, Revised 
and Illustrated. .80; Interleaved, ;^i. 25 

KIRKE. Physiology. (13th Authorized Edition, Dark Red Cloth.) 
A Hand-Book of Physiology. 13th London Edition, Revised and 
Enlarged. 516 Illustrations, some of which are printed in colors. 

Cloth, $3.25; Leather, ^4.00 

LANDOIS. A Text-Book of Human Physiology, Including 
Histology and Microscopical Anatomy, with Special Reference to 
the Requirements of Practical Medicine. 4th American, translated 
from the 7th German Edition, with Additions by Wm. Stirling, m.d., 
D.sc. 845 lUus., many of which are printed in colors. 2 Vols. $7.00 

STARLING. Elements of Human Physiology. 100 Ills. $1.00 

STIRLING. Outlines of Practical Physiology. Including 
Chemical and Experimental Physiology, with Special Reference to 
Practical Medicine. 3d Edition. 289 Illustrations. ^2.00 

TYSON. Cell Doctrine. Its History and Present State. 2d 
Edition. |i-5o 

YEO. Manual of Physiology. A Text-Book for Students of 
Medicine. By Gerald F. Yeo, m.d., f.r.c.s. 6th Edition. 254 
Illustrations and a Glossary. Cloth, $2.50 ; Leather, $3.00 

PRACTICE. 

BEALE. On Slight Ailments; their Nature and Treatment. 

2d Edition, Enlarged and Illustrated. $1.25 

CHARTERIS. Practice of Medicine. 6th Edition. Thera- 
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FAGGE. The Practice of Medicine. Cloth, $7.00 ; Leather, ^9.00 
FO'WLER. Dictionary of Practical Medicine. By various 
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HUGHES. Compend of the Practice of Medicine. 5th Edition, 
Revised and Enlarged. 

Part I. Continued, Eruptive, and Periodical Fevers, Diseases of the 
Stomach, Intestines, Peritoneum, Biliary Passages, Liver, Kid- 
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Part II. Diseases of the Respiratory System, Circulatory System, 
and Nervous System; Diseases of the Blood, etc. 

Price of each part, .80; Interleaved, $1.25 

Physician's Edition. In one volume, including the above two 

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ROBERTS. The Theory and Practice of Medicine. The 

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TAYLOR. Practice of Medicine. Cloth, $2.00; Sheep, ^2.50 

PRESCRIPTION BOOKS. 

BEASLEY. Book of 3100 Prescriptions. Collected from th 
Practice of the Most Eminent Physicians and Surgeons — English 
French, and American. A Compendious History of the Materia, 
Medica, Lists of the Doses of all Officinal and Established Prepara- 
tions, and an Index of Diseases and their Remedies. 7th Ed. ;^2.oo 



MEDICAL BOOKS. 19 



BEASLEY. Druggists' General Receipt Book. Comprising 
a Copious Veterinary Formulary, Recipes in Patent and Proprie- 
tary Medicines, Druggists' Nostrums, etc. ; Perfumery and Cos- 
metics, Beverages, Dietetic Articles and Condiments, Trade Chem- 
icals, Scientific Processes, and an Appendix of Useful Tables, 
loth Edition, Revised. ^2.00 

BEASLEY. Pocket Formulary. A Synopsis of the British and 
Foreign Pharmacopoeias. Comprising Standard and Approved 
Formulae for the Preparations and Compounds Employed in Medical 
Practice, nth Edition. Cloth, J2.00 

DAVIS. Essentials of Materia Medica and Prescription 
Writing. $150 

PEREIRA. Prescription Book. Containing Lists of Terms, 
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planatory Notes, Grammatical Construction of Prescriptions, etc. 
i6th Edition. Cloth, .75 ; Tucks, ^i.oo 

WYTHE. Dose and Symptom Book. The Physician's Pocket 
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the Principal Articles of the Materia Medica and Officinal Prepara- 
tions. 17th Ed. Cloth, .75; Leather, with Tucks and Pocket, ^i.oo 

SKIN. 

ANDERSON. A Treatise on Skin Diseases. With Special 
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of 11,000 Consecutive Cases. Illus. Cloth, $3.00; Leather, ^4.00 

BULKLEY. The Skin in Health and Disease. Illustrated. .40 

CROCKER. Diseases of the Skin. Their Description, Pathol- 
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VAN HARLINGEN. On Skin Diseases. A Practical Manual 
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SURGERY AND SURGICAL DIS- 
EASES. 

CAIRD AND CATHCART. Surgical Hand-Book. 5th Edition, 
Revised. 188 Illustrations. Full Red Morocco, $2.50 

DULLES. What to Do First in Accidents and Poisoning. 
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HACKER. Antiseptic Treatment of Wounds, Introduction to 
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Vienna. With a Photo-engraving of Billroth in his Clinic. .50 

HEATH. Minor Surgery and Bandaging. loth Ed., Revised 
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HEATH. Injuries and Diseases of the Jaws. 4th Edition. 
187 Illustrations. i^4-5o 

HEATH. Lectures on Certain Diseases of the Jaws. 64 Illus- 
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HORWITZ. Compend of Surgery and Bandaging, including 
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ranged. 167 Illustrations, 98 Formulae. Clo., .80; Interleaved, $1.25 



20 SUBJECT CATALOGUE. 



JACOBSON. Operations of Surgery. Over 200 Illustrations. 

Cloth, $3.00 ; Leather, ^4.00 

JACOBSON. Diseases of the Male Organs of Generation. 

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MACREADY. A Treatise on Ruptures. 24 Full-page Litho- 
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MOULLIN. Text-Book of Surgery. With Special Reference to 
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met." — The Aiiierican Jour^ial of Medical Science. 

PORTER. Surgeon's Pocket-Book. 3d Ed. Lea. Cover, $2.00. 

SMITH. Abdominal Surgery. Being a Systematic Description of 
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VOSWINKEL. Surgical Nursing, in Illustrations. $i.oo 

WALSHAM. Manual of Practical Surgery. 5th Ed., Re- 
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WATSON. On Amputations of the Extremities and Their 
Complications. 250 Illustrations. ^5-5o 

THROAT AND NOSE (see also Ear). 

COHEN. The Throat and Voice. Illustrated. .40 

HALL. Diseases of the Nose and Throat. Two Colored 
Plates and 59 Illustrations. $2.50 

HALL. Compend of Diseases of the Ear and Nose. Illus- 
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HUTCHINSON. The Nose and Throat. Including the Nose, 
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MACKENZIE. The Pharmacopoeia of the London Hospital 
for Diseases of the Throat. 5th Edition, Revised by Dr. F. 
G. Harvey. ^i.oo 

McBRIDE. Diseases of the Throat, Nose, and Ear. A Clinical 
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MURRELL. Chronic Bronchitis and its Treatment. (Author- 
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POTTER. Speech and its Defects. Considered Physiologically, 
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WOAKES. Post-Nasal Catarrh and Diseases of the Nose 
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URINE AND URINARY ORGANS. 

ACTON. The Functions and Disorders of the Reproductive 
Organs in Childhood, Youth, Adult Age, and Advanced Life, 
Considered in their Physiological, Social, and Moral Relations. 
8th Edition. ^1.75 

ALLEN. Albuminous and Diabetic Urine. $2.25 



MEDICAL BOOKS. 21 



BEALE. One Hundred Urinary Deposits. On eight sheets, 
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HOLLAND. The Urine, the Gastric Contents, the Common 
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LEGG. On the Urine. 7th Edition, Enlarged, lllus, ^i.oo 

MARSHALL AND SMITH. Analysis of Urine. $1.00 

MEMMINGER. Diagnosis by the Urine. 23 lllus. ^i.co 

MOULLIN. Enlargement of the Prostate. Its Treatment and 
Radical Cure, illustrated. $1.50 

THOMPSON. Diseases of the Urinary Organs. 8th Ed. $3.00 
THOMPSON. Calculous Diseases. The Preventive Treatment 
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TYSON. Guide to Examination of the Urine. For the Use of 
Physicians and Students. With Colored Plate and Numerous Illus- 
trations engraved on wood. 8th Edition, Revised. $1.25 
VAN NUYS. Chemical Analysis of Healthy and Diseased 
Urine, Qualitative and Quantitative. 39 Illustrations. ^i.oo 

VENEREAL DISEASES. 

COOPER. Syphilis. 2d Edition, Enlarged and Illustrated with 
20 full-page Plates. $5.00 

GOWERS. Syphilis and the Nervous System. $1.00 

HILL AND COOPER. Venereal Diseases. Being a Concise De- 
scription of Those Affections and Their Treatment. 4th Ed. .75 

JACOBSON, Diseases of the Male Organs of Generation. 88 
Illustrations. ^6.00 

VETERINARY. 

ARMATAGE. The Veterinarian's Pocket Remembrancer. 

Being Concise Directions for the Treatment of Urgent or Rare Cases, 
Embracing Semeiology, Diagnosis, Prognosis, Surgery, Treatment, 
etc, 2d Edition, Boards, $1.00 

BALLOU. Veterinary Anatomy and Physiology. 29 Graphic 
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TUSON. Veterinary Pharmacopoeia. Including the Outlines of 
Materia Medica and Therapeutics. 5th Edition. 1^2.25 

\A^OMEN, DISEASES OF. 

BYFORD (H. T.). Manual of Gynecolog;y. With 234 Illustra- 
tions, many of which are from original drawings and photographs. 
Just Ready. ^2.50 

BYFORD (W. H.). Diseases of Women. 4th Edition. 306 
Illustrations. Cloth, ^2.00 ; Leather, ^2.50 

DUHRSSEN. A Manual of Gynecological Practice. 105 
Illustrations. Just Ready. ^1.50 

LEWERS. Diseases of Women. 146 lUus, 3d Edition. $2.00 

WELLS. Compend of Gynecology. lllus. .80; Interleaved, ^1.25 

WINCKEL. Diseases of Women. Translated by special authority 

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Theophilus Parvin, m.d. 152 Engravings on Wood. 2d Edition, 

Revised. Cloth, ^3,00 ; Leather, 1^3.50 

FULLERTON. Nursing in Abdominal Surgery and Diseases 

of Women. 2d Edition. 70 Illustrations. ^150 



22 SUBJECT CATALOGUE. 

COMPENDS. 



From The ^^outher 71 Clinic. 

"We know of no series of books issued by any house that so fully 
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ranged, full, and concise, and are really the best line of text-books that 
could be found for either student or practitioner." 



BLAKISTON^S ? QUIZ-COMPENDS? 

The Best Series of Manuals for the Use of Students. 
Price of each, Cloth, .80. Interleaved, for taking Notes, $1.25. 

4^ These Compends are based on the most popular text-books 
and the lectures of prominent professors, and are kept constantly re- 
vised, so that they may thoroughl}'- represent the present state of the 
subjects upon which they treat. 

4^ The authors have had large experience as Quiz-Masters and 
attaches of colleges, and are well acquainted with the wants of students. 

j|^* They are arranged in the most approved form, thorough and 
concise, containing over 6oo fine illustrations, inserted wherever they 
could be used to advantage. 

4®=* Can be used by students of any college. 

j|^ They contain information nowhere else collected in such a 
condensed, practical shape. Illustrated Circular free. 

No. I. POTTER. HUMAN ANATOMY. Fifth Revised and 

Enlarged Edition. Including Visceral Anatomy. Can be used 
with either Morris's or Gray's Anatomy. 117 Illustrations and 16 
Lithographic Plates of Nerves and Arteries, with Explanatorj'^ 
Tables, etc. By Samuel O. L. Potter, m.d.. Professor of the 
Practice of Medicine, Cooper Medical College, San Francisco ; late 
A. A. Surgeon, U. S. Army. 
No. 2. HUGHES. PRACTICE OF MEDICINE. Part I. Fifth 
Edition, Enlarged and Improved. By Daniel E. Hughes, m.d., 
Physician-in-Chief, Philadelphia Hospital, late Demonstrator of 
Clinical Medicine, Jefferson Medical College, Phila. 

No. 3. HUGHES. PRACTICE OF MEDICINE. Part II. 

Fifth Edition, Revised and Improved. Same author as No. 2. 

No. 4. BRUBAKER. PHYSIOLOGY. Seventh Edition, with 
new Illustrations and a table of Physiological Constants. Enlarged 
and Revised. By A. P. Brubaker, m.d., Professor of Physiology 
and General Pathology in the Pennsylvania College of Dental 
Surgery ; Demonstrator of Physiology, Jefferson Medical College, 
Philadelphia. 

No. 5. LANDIS. OBSTETRICS. Fifth Edition. By Henry G. 
Landis, m.d. Revised and Edited by Wm. H. Wells, m.d.. 
Assistant Demonstrator of Obstetrics, Jefferson Medical College, 
Philadelphia. Enlarged. 47 Illustrations. 

No. 6. POTTER. MATERIA MEDICA, THERAPEUTICS, 
AND PRESCRIPTION WRITING. Sixth Revised Edition 
(U. S. P. 1890). By Samuel O. L. Potter, m.d.. Professor of 
Practice, Cooper Medical College, San Francisco ; late A. A. Sur- 
geon, U. S. Army. 



MEDICAL BOOKS. 



PQUIZ-COMPENDS ?— Continued. 

No. 7. WELLS. GYNECOLOGY. A New Book. By Wm. 
H. Wells, m.d. Assistant Demonstrator of Obstetrics, Jefferson 
College, Philadelphia. Illustrated. 

No. 8. FOX AND GOULD. DISEASES OF THE EYE AND 
REFRACTION. Second Edition. Including Treatment and 
Surs;ery. By L. Webster Fox, m.d., and George M. Gould, 
M.D. With 39 Formulae and 71 Illustrations. 

No. 9. HORWITZ. SURGERY, Minor Surgery, and Bandag- 
ing. Fifth Edition, Enlarged and Improved. By Orville 
HoRWiTZ, B. s., M.D., Clinical Professor of Genito-Urinary Surgery 
and Venereal Diseases in Jefferson Medical College ; Surgeon to 
Philadelphia Hospital, etc. With 98 Formulae and 71 Illustrations. 

No. 10. LEFFMANN. MEDICAL CHEMISTRY. Fourth 

Edition. Including Urinalysis, Animal Chemistry, Chemistry of 
Milk, Blood, Tissues, the Secretions, etc. By Henry Leffmann, 
M D., Professor of Chemistry in Pennsylvania College of Dental 
Surgery and in the Woman's Medical College, Philadelphia. 

No. II. STEWART. PHARMACY. Fifth Edition. Based upon 
Prof. Remington's Text-Book of Pharmacy. By F. E. Stewart, 
m d., ph.g., late Quiz-Master in Pharmacy and Chemistry, Phila- 
delphia College of Pharmacy ; Lecturer at Jefferson Medical 
College. Carefully revised in accordance with the new U. S. P. 

No. 12. BALLOU. VETERINARY ANATOMY AND PHY- 
SIOLOGY. Illustrated. By Wm. R. Ballou, m.d.. Professor 
of Equine Anatomy at New York College of Veterinary Surgeons ; 
Physician to Bellevue Dispensary, etc. 29 graphic Illustrations. 

No. 13. WARREN. DENTAL PATHOLOGY AND DEN- 
TAL MEDICINE. Second Edition, Illustrated. Containing 
all the most noteworthy points of interest to the Dental Student 
and a Section on Emergencies. By Geo. W. Warren, d.d.s.. 
Chief of Clinical Staff, Pennsylvania College of Dental Surgery, 
Philadelphia. 

No. 14. HATFIELD. DISEASES OF CHILDREN. Second 
Edition. Colored Plate. By Marcus P. Hatfield, Profes- 
sor of Diseases of Children, Chicago Medical College. 

No. 15. HALL. GENERAL PATHOLOGY AND MORBID 
ANATOMY. 91 Illustrations. By H. Newberry Hall, ph.g., 
m.d., Professor of Pathology and Med. Chem., Chicago Post- 
Graduate Medical School ; Mem. Surgical Staff, Illinois Charit- 
able Eye and Ear Infirmary; Chief of Ear Clinic, Chicago Med. 
College. 

No. 16. DISEASES OF NOSE AND EAR. Illustrated. Same 
Author as No. 15. 

Price, each, Cloth, .80. Interleaved, for taking Notes, $1,25. 

Handsome Illustrated Circular sent free upon application. 

In preparing, revising, and improving Blakiston's ? Quiz-Com- 
pends ? the particular wants of the student have always been kept in 
mind. 

Careful attention has been given to the construction of each sentence, 
and while the books will be found to contain an immense amount of 
knowledge in small space, they will likewise be found easy reading ; 
there is no stilted repetition of words ; the style is clear, lucid, and dis- 
tinct. The arrangement of subjects is systematic and thorough ; there 
is a reason for every word. They contain over 600 illustrations. 



The following books in this Catalogue 

ARE SPECIALLY RECOMMENDED 

TO 

MEDICAL STUDENTS 

as being of a character to help the student in his work with- 
out interfering with the regular text books : — 

HOLDEN'S DISSECTOR. Page 3. 

A manual of dissections, handsomely illustrated, clear and com- 
pact. Comes bound in oil-cloth for those who prefer it. 

HARTLEY'S MEDICAL CHEMISTRY. Page 4. 

A compact manual, prepared specially for medical and pharma- 
ceutical students. Revised in accordance with the last edition of 
the U. S. P. and the late text-books on materia medica and thera- 
peutics. 

OMEROD'S NERVOUS DISEASES. Page 15. 

Designed as an introduction to the more elaborate text-books. 

GOULD'S DICTIONARIES. Page 8. 

The most complete and best medical dictionaries, containing a 
large amount of tabulated and concisely arranged information. A 
sale of 40,000 copies attest to their great value. 

DAVIS' OBSTETRICS. Page 16. 

A very complete manual, containing a large number of practical 
illustrations. The second edition has been carefully revised and 
enlarged. 

BYFORD'S GYNECOLOGY. Page 21. 

A practical hand-book, thoroughly illustrated with over two hun- 
dred figures. Concise and up to date. 

VAN HARLINGEN'S SKIN DISEASES. Page 19. 

A third edition just ready. Revised throughout, with many new 
illustrations. 

TYSON'S PHYSICAL DIAGNOSIS. Page 17. 

Second edition, illustrated, will be found exceedingly useful by the 
student of clinical medicine. 

BLAKISTON'S .? QUIZ-COMPENDS ?. Page 22. 

Sixteen practical books dealing with the various branches of 
study — anatomy, physiology, practice, materia medica and thera- 
peutics, pathology, etc., etc. These books have been written by 
quiz-masters, demonstrators, and professors in medical schools who 
thoroughly understand the wants of students. Price of each, 80 
cents, strongly bound in durable brown cloth. A special illustrated 
circular will be sent upon application. 



